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Record Type: Instruction
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Directive Number: CPL 2.106
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Subject: Enforcement Procedures and Scheduling for Occupational
Exposure to Tuberculosis
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Information Date: 02/09/1996
OSHA Instruction CPL 2.106
February 9, 1996
Office of Health Compliance Assistance
SUBJECT: Enforcement Procedures and Scheduling for Occupational Exposure
to Tuberculosis
A. Purpose. This instruction provides uniform inspection procedures
and guidelines to be followed when conducting inspections and issuing citations
under Section 5(a)(1) of the OSH Act and pertinent standards for employees
who are occupationally exposed to tuberculosis.
B. Scope. This instruction applies OSHA-wide.
C. References.
1. OSHA Instruction CPL 2.103, September 26, 1994, Field Inspection
Reference Manual (FIRM).
2. OSHA Instruction CPL 2.45B, June 15, 1985, The Revised Field Operations
Manual (FOM).
3. American Public Health Association - 1990 or current edition, Control
of Communicable Diseases in Man.
4. OSHA Instruction CPL 2-2.20B, CH-3, August 22, 1994. Occupational
Safety and Health Administration Technical Manual Chapter No. 7.
5. OSHA Instruction, ADM 1-31, the IMIS Enforcement Data Processing
Manual.
6. OSHA Instruction ADM 1-32, Enforcement User Skills Manual (for those
Area Offices still using the NCR system).
7. Centers for Disease Control and Prevention (CDC), Biosafety in Microbiological
and Biomedical Laboratories, 3rd Edition, or current edition.
8. Department of Health and Human Services, Public Health Service, 42
CFR Part 84; Final Rule
9. Centers for Disease Control and Prevention (CDC); Guidelines for
Preventing the transmission of mycobacterium tuberculosis in Health Care
Facilities, 1994; MMWR October 26, 1994 Vol. 43, No. RR-13.
D. Action. OSHA Regional Administrators and Area Directors shall
use this instruction to ensure uniformity when performing inspections for
occupational exposures to tuberculosis (TB). The Directorate of Compliance
Programs shall provide support as necessary to assist the Regional Administrators
and Area Directors in enforcing this directive. Issuance of this directive
cancels the Memorandum to Regional Administers dated October 8, 1993, and
entitled Enforcement Policy and Procedures for Occupational Exposure to
Tuberculosis.
E. Federal Program Change. This is a federal program change which
impacts state programs.
1. The Regional Administrator (RA) shall ensure that this change is
promptly forwarded to each state designee using a format consistent with
the Plan Change Two-way Memorandum in Appendix A, State Plan Policies and
Procedures Manual (SPM).
2. The RA shall explain the content of this change to the state designee
as required.
3. The state shall respond to this change within 70 days in accordance
with paragraph I.1.a.(2).(a). and (b)., Part I, Chapter III of the SPM.
4. The state's acknowledgment shall include (a) the state's plan to
adopt and implement an identical change, (b) the state's plan to develop
an alternative, which is as effective, or the reasons why no change is
necessary to maintain a program which is as effective. The state shall
submit a plan supplement within six months in accordance with I.1.a.(3).(c).,
Part I, Chapter III of the SPM.
5. The RA shall advise state designees of the following:
a. In order to ensure a sound and consistent national enforcement and
litigation strategy in relation to complex issues addressed by this instruction,
state implementation of the procedures in this instruction, or comparable
state procedures, must be carefully coordinated with OSHA.
b. The state is also responsible for extending coverage under its procedures
for addressing occupational exposure to tuberculosis to the public sector
employees in workplaces covered by this instruction.
c. The Directorate of Technical Support is available to assist the states
in locating expert witnesses (see paragraph M., expert witnesses). Also,
the Directorate of Compliance Programs will provide support to the states
through the RA to assist in the enforcement of this directive.
6. The RA shall review policies, instructions, and guidelines issued
by the state to determine that this change has been communicated to state
compliance personnel.
F. Definitions. For a complete list of definitions applicable
to tuberculosis please refer to the list of definitions in the 1994 CDC
guidelines found in Appendix A beginning on page 113.
G. Background. Since 1985, the incidence of tuberculosis (TB)
in the general U.S. population has increased approximately 14 percent,
reversing a 30-year downward trend. In 1993, 25,313 new cases of TB were
reported in the United States. Increases in the incidence of TB have been
observed in some geographic areas; these increases are related partially
to the high risk for TB among immunosuppressed persons, particularly those
infected with human immunodeficiency virus (HIV). Other factors (e.g.,
socioeconomic) have also contributed to these increases. Outbreaks have
occurred in hospitals, correctional institutions, homeless shelters, nursing
homes, and residential care facilities for AIDS patients. During 1994 and
1995 there has been a decrease in the number of TB cases in the United
States that is likely been due to increased awareness and efforts in the
prevention and control of TB, including the implementation of TB control
measures recommended by the CDC and required by OSHA.
Recently, drug resistant strains of M. tuberculosis have become a serious
concern and cases of multi-drug-resistant (MDR) TB have occurred in forty
states. In a recent New York City study, 33% of cases had organisms resistant
to the two most effective drugs available for treating the disease.
When organisms are resistant to both drugs, the course of the treatment
increases from six months to 18-24 months, and the cure rate decreases
from 100% to 60% or less.
In a 1992 American Hospital Association survey/CDC survey, 90 of 729
(13%) respondents reported nosocomial TB transmission to health care workers.
More than 80% of those facilities experienced TB skin test conversions
among workers. More than 100 cases of active TB disease in health care
workers were known to CDC and reported to Congress by Dr. William Roper
in the Spring of 1993. Twelve (12) health care workers have died. Nationwide,
at least several hundred employees have become infected and required medical
treatment after workplace exposure to TB. In general, persons who become
infected with TB have approximately a 10% risk for developing active TB
in their lifetimes.
M. tuberculosis is carried through the air in tiny infectious droplet
nuclei of 1 to 5 microns in diameter. These droplets may be generated when
a person with pulmonary and laryngeal TB disease coughs, speaks, sings,
sneezes, or spits. When inhaled by susceptible persons, the mycobacteria
in these droplets may become established in the lungs and, in some cases,
spread throughout the body. After an interval of months, years, or even
decades, the initial infection may then progress to clinical illness (i.e.,
tuberculosis disease). Transmission of TB is most likely to occur from
persons with pulmonary or laryngeal TB that are not on effective anti-TB
therapy and who have not been placed in respiratory isolation.
In occupational healthcare settings, where patients with TB are seen,
workers exposed to tuberculosis droplet nuclei are at increased risk of
infection with exposure to TB. Certain high-risk medical procedures that
are cough-inducing or aerosol generating can further increase the risk
of infection in health-care workers.
The employer's obligations are those set forth in the Occupational Safety
and Health Act (OSH Act) of 1970. Recommendations for preventing the transmission
of TB for health care settings were originally established with the 1990
CDC Guidelines. In October, of 1994, those guidelines were revised and
published (Appendix A). The new guidelines emphasize the control of TB
through an effective TB infection control program. Under these guidelines
the control of TB is to be accomplished through the early identification,
isolation, and treatment of persons with TB, use of engineering and administrative
procedures to reduce the risk of exposure, and through the use of respiratory
protection. OSHA believes these guidelines reflect an industry recognition
of the hazard as well as appropriate, widely recognized, and accepted standards
of practice to be followed by employers in carrying out their responsibilities
under the OSH Act.
H. Inspection Scheduling and Scope
1. The evaluation of occupational exposure to TB shall be conducted
in response to employee complaints, related fatality/catastrophes, or as
part of all industrial hygiene inspections conducted in workplaces where
the CDC has identified workers as having a greater incidence of TB infection
than in the general population. The degree of risk of occupational exposure
of a worker to TB will vary based on a number of factors discussed in detail
by the CDC (Appendix A, pg. 4-5). These workplaces have been the subject
of reports issued by the CDC which provide recommendations for the control
of tuberculosis. Specifically, these workplaces are as follows:
a. health care facilities b. correctional institutions c. long-term
care facilities for the elderly d. homeless shelters e. drug treatment
centers
Note: Health-care facilities include hospitals where patients
with confirmed or suspect TB are treated or to which they are transported.
Coverage of non-hospital health care settings (i.e., doctors' offices,
clinics, etc.) includes only personnel present during the performance of
high hazard procedures on suspect or active TB patients. Dental health
care personnel are covered by the directive only if they treat suspect
or active patients in a hospital or correctional facility.
Homeless shelters - due to a variety of circumstances, the control of
TB in homeless shelters presents unique problems for the protection of
workers. Shelters must establish protocols that provide for rapid early
identification followed by immediate transfer of suspect cases if the shelters
have elected not to treat these patients.
2. All inspections in these workplaces shall include a review of the
employer's plans for employee TB protection, if any. Such plans may include
the infection control program, respiratory protection and skin testing.
Employee interviews and site observations are an integral part of the process
evaluation.
3. Complaints received from state and local government employees who
are outside federal jurisdiction in federal enforcement states shall be
referred to the appropriate agency by the Area Office.
I. Inspection Procedures. The procedure given in the FIRM, Chapter
II, shall be followed except as modified in the following sections:
1. Health care facilities generally have internal infection control
and employee health programs. This function may be performed by a team
or individual. Upon entry, the CSHO shall request the presence of the infection
control director and employee occupational health professional responsible
for occupational health hazard control. Other individuals who will be responsible
for providing records pertinent to the inspection may include: training
director, facilities engineer, director of nursing, etc.
2. The CSHO shall establish whether or not the facility has had a suspect
or confirmed TB case within the previous six (6) months from the opening
conference to determine coverage under the OSH Act. This determination
may be based upon interviews and, in a hospital, a review of the infection
control data.
3. If the facility has had a suspect or confirmed TB case within the
previous six months, the CSHO shall proceed with the TB portion of the
inspection. The CSHO shall verify implementation of the employer's plans
for TB protection through employee interviews and direct observation where
feasible. Professional judgment shall be used to identify which areas of
a facility must be inspected during the walkthrough (e.g., emergency rooms,
respiratory therapy areas, bronchoscopy suites, and morgue). After review
of the facility plans for worker TB protection, employee interviews combined
with an inspection of appropriate areas of the facility, shall be used
to determine compliance.
4. CSHOs who perform smoke-trail visualization tests should review the
protocol in Appendix B of this directive.
5. CSHOs should be prepared to present to the employer the material
safety data sheet (MSDS) for the smoke that is released on a smoke-trail
visualization.
J. Compliance Officer Protection
1. Area Directors or Assistant Area Directors shall ensure that CSHOs
performing TB related inspections are familiar with the CDC Guidelines,
terminology, and are adequately trained through either course work or field/work
experience in health care settings. Consultation with the regional TB coordinators
is encouraged prior to beginning such inspections.
2. CSHOs shall not enter occupied respiratory isolation [AFB (acid fast
bacilli)] rooms to evaluate compliance unless, in their determination entry
is required to document a violation. Prior to entry CSHOs will discuss
the need for entry with the Area Director. Photographs or video taping
where practical shall be used for case documentation. Under no circumstances
shall photographing or videotaping of patients be done. CSHO's must take
all necessary precautions to assure and protect patient confidentiality.
3. CSHOs shall exercise professional judgement and extreme caution when
engaging in activities that may involve potential exposure to TB. CSHOs
normally shall establish the existence of hazards and adequacy of work
practices through employee interviews and shall observe them in a manner
which prevents exposure (e.g., through an observation window where available).
4. On rare occasions when entry into potentially hazardous areas is
judged necessary (e.g., where the CSHO determines that direct observation
of a high hazard procedure is necessary), the CSHO shall be properly equipped
as required by the facility, this directive, and following consultation
with the CSHO's supervisor. Since CSHOs' respiratory protection is used
in more than one type of industry they shall use their negative pressure
elastomeric face piece respirators equipped with HEPA filters as the minimum
level of respiratory protection.
5. CSHOs who conduct TB inspections shall have been offered the TB skin
tests. CSHOs exposed to an individual(s) with active infectious TB shall
receive a follow-up examination and follow Sections J. and K. of Appendix
A beginning on page 37.
Note: A "TB Skin Test" means the intradermal injection (Mantoux Method)
of tuberculin antigen (usually PPD) with subsequent measurement of the
induration by designated, trained personnel.
6. If an isolation room is occupied by a patient with confirmed or suspect
TB or has not been adequately purged when a smoke-trail test is performed,
then the CSHO should assume that the isolation room is not under negative
pressure. Under such circumstances CSHOs shall wear a negative pressure
HEPA respirator when performing air tests as described in Appendix B or
if entry into the room is determined to be necessary.
K. Citation Policy. Relevant chapters of the FIRM shall be followed
when preparing and issuing citations for hazards related to TB.
1. The following requirements apply when citing hazards found in target
workplaces. Employers must comply with the provisions of these requirements
whenever an employee may be occupationally exposed to TB:
Section 5(a)(1) -- General Duty Clause and Executive Order 12196, Section
1-201(a) for Federal facilities.
29 CFR 1910.134 -- Respiratory Protection
29 CFR 1910.145 -- Accident Prevention Signs and Tags
29 CFR 1910.20 -- Access to Employee Exposure and Medical Records
29 CFR 1904 -- Recording and Reporting Occupational Injuries & Illness
L. Violations. All elements in this section must be addressed
to ensure adequate protection of employees from TB hazards. Violations
of these OSHA requirements will normally be classified as serious.
1. General Duty Clause - Section 5(a)(1). Section 5(a)(1) provides:
"Each employer shall furnish to each of his employees employment and a
place of employment which are free from recognized hazards that are causing
or are likely to cause death or serious physical harm to his employees."
a. Section 5(a)(1) citations must meet the requirements outlined in
the FIRM, and shall be issued only when there is no standard that applies
to the particular hazard. The hazard, not the absence of a particular means
of abatement, is the basis for a general duty clause citation. All applicable
abatement methods identified as correcting the same hazard shall be issued
under a single 5(a)(1) citation.
b. Recognition, for purposes of citing section 5(a)(1), is shown by
the CDC Guidelines for the types of exposures detailed below because the
CDC is an acknowledged body of experts familiar with the hazard.
c. Citations shall be issued to employers with employees working in
one of the workplaces where the CDC has identified workers as having a
higher incidence of TB infection than the general population, when the
employees are not provided appropriate protection and who have exposure
as defined below:
1. Exposure to the exhaled air of an individual with suspected or confirmed
pulmonary TB disease, or
Note: A suspected case is one in which the facility has identified
an individual as having symptoms consistent with TB. The CDC has identified
the symptoms to be: productive cough, coughing up blood, weight loss, loss
of appetite, lethargy/weakness, night sweats, or fever.
2. Employee exposure without appropriate protection to a high hazard
procedure performed on an individual with suspected or confirmed infectious
TB disease and which has the potential to generate infectious airborne
droplet nuclei. Examples of high hazard procedures include aerosolized
medication treatment, bronchoscopy, sputum induction, endotracheal intubation
and suctioning procedures, emergency dental, endoscopic procedures, and
autopsies conducted in hospitals.
d. If a citation under 5(a)(1) is justified, the citation, after setting
forth the SAVE for section 5(a)(1), shall state:
Section 5(a)(1) of the Occupational Safety and Health Act of 1970: The
employer did not furnish employment and a place of employment which were
free from recognized hazards that were causing or likely to cause death
or serious physical harm to employees exposed to the hazard of being infected
with Mycobacterium tuberculosis through unprotected contact with [specify
group such as patients, inmates, clients, etc.] who was/were infectious
or suspected to be infectious with tuberculosis in that: [list deficiencies]
Feasible and useful abatement methods for reducing this hazard, as recommended
by the CDC, include, but are not limited to: [list abatement methods].
e. The following are examples of feasible and useful abatement methods,
which must be implemented to abate the hazard. Deficiencies found in any
category can result in the continued existence of a serious hazard and
may, therefore, allow citation under 5(a)(1).
1. Early Identification of Patient/Client. The employer shall
implement a protocol for the early identification of individuals with active
TB. See Appendix A pages 19-30.
2. Medical Surveillance:
a. Initial Exams. The employer, in covered workplaces, shall offer TB
skin tests (at no cost to the employees) to all current potentially exposed
employees and to all new employees prior to exposure. A two-step baseline
shall be used for new employees who have an initially negative PPD test
result and who have not had a documented negative TB skin test result during
the preceding 12 months (See Appendix A, pg. 63). TB skin tests shall be
offered at a time and location convenient to workers. Follow-up and treatment
evaluations are also to be offered at no cost to the workers.
Note: The reading and interpretation of the TB skin tests shall
be performed by a qualified individual as described in the CDC Guidelines.
b. Periodic Evaluations. TB skin testing shall be conducted every three
(3) months for workers in high risk categories, every six (6) months for
workers in intermediate risk categories, and annually for low risk personnel
(The CDC has defined the criteria for high, intermediate, and low risk
categories, see Appendix A, pg. 8-17). Workers with a documented positive
TB skin test who have received treatment for disease or preventive therapy
for infection are exempt from the TB skin test but must be informed periodically
about the symptoms of TB and the need for immediate evaluation of any pulmonary
symptoms suggestive of TB by a physician or trained health care provider
to determine if symptoms of TB disease have developed.
Note: If the facility has not completed a risk assessment the CSHO shall
review the TB related records to establish required testing frequencies
for the facility and areas of the facility.
c. Reassessment following exposure or change in health. Workers who
experience exposure to an individual with suspect or confirmed infectious
TB for whom infection control precautions have not been taken shall be
managed according to CDC recommendations (Appendix A). An employee who
develops symptoms of TB disease shall be immediately evaluated according
to the CDC Guidelines.
3. Case Management of Infected Employees shall include the
following:
a. Protocol for New Converters. Conversion to a positive TB skin test
shall be followed as soon as possible, by appropriate physical, laboratory,
and radiographic evaluations to determine whether the employee has infectious
TB disease. (See Appendix A, pg. 65).
b. Work Restrictions for Infectious Employees. See Appendix A, page
41.
4. Worker Education and Training. Training and information to
ensure employee knowledge of such issues as the mode of TB transmission,
its signs and symptoms, medical surveillance and therapy, and site specific
protocols including the purpose and proper use of controls shall be provided
to all current employees and to new workers upon hiring. (See Appendix
A, pgs. 36-37) Training should be repeated as needed.
Workers shall be trained to recognize, and report to a designated person,
any patients or clients with symptoms suggestive of infectious TB and instructed
on the post exposure protocols to be followed in the event of an exposure
incident. (See Appendix A, pg. 23)
5. Engineering Controls. The use of each control measure must
be based on its ability to abate the hazard.
a. Individuals with suspected or confirmed infectious TB disease must
be placed in a respiratory acid-fast bacilli (AFB) isolation room. High
hazard procedures on individuals with suspected or confirmed infectious
TB disease must be performed in AFB treatment rooms, AFB isolation rooms,
booths, and/or hoods. AFB isolation refers to a negative pressure room
or an area that exhausts room air directly outside or through HEPA filters
if recirculation is unavoidable.
b. Isolation and treatment rooms in use by individuals with suspected
or confirmed infectious TB disease shall be kept under negative pressure
to induce airflow into the room from all surrounding areas (e.g., corridors,
ceiling plenums, plumbing chases, etc.). (See Appendix A, Supplement No.
3, page 76)
Note: The employer must assure that AFB isolation rooms are maintained
under negative pressure. At a minimum, the employer must use nonirritating
smoke trails or some other indicator to demonstrate that direction of airflow
is from the corridor into the isolation/treatment room with the door closed.
If an anteroom exists, direction of airflow must be demonstrated at the
inner door between the isolation/treatment room and the anteroom. (See
Appendix B)
c. Air exhausted from AFB isolation or treatment rooms must be safely
exhausted directly outside and not recirculated into the general ventilation
system. (See Appendix A, Supplement No. 3, page 87).
In circumstances where recirculation is unavoidable, HEPA filters must
be installed in the duct system from the room to the general ventilation
system. (See Appendix A, Supplement No. 3, page 82). For these HEPA filters,
a regularly scheduled monitoring program to demonstrate as-installed effectiveness
should include; 1) recognized field test method, 2) acceptance criteria,
and 3) testing frequencies (see Appendix A, Supplement No. 3, page 85).
The air handling system should be appropriately marked with a TB warning
where maintenance personnel would have access to the duct work, fans, or
filters for maintenance or repair activities.
d. In order to avoid leakage, all potentially contaminated air which
is ducted through the facility must be kept under negative pressure until
it is discharged safely outside (i.e., away from occupied areas and air
intakes), or
e. The air from isolation and treatment rooms must be decontaminated
by a recognized process (e.g., HEPA filter) before being recirculated back
to the isolation/treatment room. The use of UV radiation as the sole means
of decontamination shall not be used. The CDC Guidelines allow the use
of UV in waiting rooms, emergency rooms, corridors, and the like where
patients with undiagnosed TB could potentially contaminate the air. (See
appendix A, pg. 90)
Note: The opening and closing of doors in an isolation or treatment
room which is not equipped with an anteroom compromises the ability to
maintain negative pressure in the room. For these rooms, the employer should
utilize a combination of controls and practices to minimize spillage of
contaminated air into the corridor. Recognized controls and practices include,
but are not limited to: minimizing entry to the room; adjusting the hydraulic
closer to slow the door movement and reduce displacement effects; adjusting
doors to swing into the room where fire codes permit; avoiding placement
of room exhaust intake near the door; etc.
f. If high-hazard procedures are performed within AFB isolation or treatment
rooms without benefit of source control ventilation or local exhaust ventilation
(e.g., hood, booth, tent, etc.), and droplets are released into the environment
(e.g., coughing), then a purge time interval must be imposed during which
personnel must use a respirator when entering the room. (See Appendix A,
pg. 35 and Suppl. 3, Table S3-1)
g. Interim or supplemental ventilation units equipped with HEPA filters
as described in Appendix A pgs. 70-73 are acceptable.
2. Respiratory Protection - 29 CFR 1910.134(a)(2) and (b). The
standard provides in part:
"Respirators shall be provided by the employer when such equipment is
necessary to protect the health of the employee. The employer shall provide
the respirators which are applicable and suitable for the purpose intended.
The employer shall be responsible for the establishment and maintenance
of a respiratory protective program which shall include the requirement
outlined in paragraph (b) of this section."
a. Requirements for a minimal acceptable program. The 1994 CDC
Guidelines specify standard performance criteria for respirators for exposure
to TB. These criteria include (see appendix A pg 97):
1. The ability to filter particles 1 um in size in the unloaded state
with a filter efficiency of greater than or equal to 95% (i.e., filter
leakage of less than or equal to 5%), given flow rates of up to 50L per
minute.
2. The ability to be qualitatively or quantitatively fit tested in a
reliable way to obtain a face-seal leakage of less than or equal to 10%.
3. The ability to fit the different facial sizes and characteristics
of health care workers which can usually be met by making the respirators
available in at least three sizes.
4. The ability to be checked for face piece fit, in accordance with
OSHA standards and good industrial hygiene practice, by health care workers
each time they put on their respirator.
b. Under the new NIOSH criteria, filter materials would be tested at
a flow rate of 85 L/minute for penetration by particles with a median aerodynamic
diameter of 0.3 um and, if certified would be placed in one of the following
categories: Type 100 (99.7% efficient), Type 99 (99% efficient), and Type
95 (95% efficient). NIOSH has determined that these categories of respirators
are effective against TB. Based upon these criteria, the minimally acceptable
level of respiratory protection for TB is the Type 95 Respirator. The classes
of these air-purifying, particulate respirators to be certified are described
under 42 CFR Part 84 Subpart K. See Volume 60 of the Federal Register,
page 30338 (June 8, 1995). Until these classes of respirators are commercially
available the minimal acceptable respiratory protection meeting the criteria
will remain the HEPA respirator (see Appendix A, pg 98). The following
respiratory protection measures must be addressed:
1. Employees wear HEPA or respirators certified under 42 CFR Part 84
Subpart K in the following circumstances:
a. When workers enter rooms housing individuals with suspected or confirmed
infectious TB.
b. When workers are present during the performance of high hazard procedures
on individuals who have suspected or confirmed infectious TB.
c. When emergency-medical-response personnel or others transport, in
a closed vehicle, an individual with suspected or confirmed infectious
TB.
Note: If a facility chooses to use disposable respirators as
part of their respiratory protection program, their reuse by the same health
care worker is permitted as long as the respirator maintains its structural
and functional integrity and the filter material is not physically damaged
or soiled. The facility must address the circumstances in which a disposable
respirator will be considered to be contaminated and not available for
reuse.
2. The following sample language is provided for citations which are
warranted under 1910.134(a)(2):
"The employer did not provide respirators which were applicable and
suitable for the purpose intended, nor was a respiratory protection program
established which included the requirements outlined in 29 CFR 1910.134(b):
(a) Employees were given a [surgical mask or list manufacturer/model
number] respirator for protection against airborne Mycobacterium tuberculosis
when entering isolation rooms or performing high hazard procedures [including
vehicular transporting if applicable]. They shall use NIOSH approved respirators
(HEPA or those certified under 42 CFR Part 84 Subpart K).
NIOSH approved respirators providing greater protection would also be
acceptable.
3. When respiratory protection (including disposable respirators) is
required, a complete respiratory protection program must be in place in
accordance with 29 CFR 1910.134(b).
3. Access to employee medical and exposure records: 29 CFR 1910.20.
a. A record concerning employee exposure to TB is an employee exposure
record within the meaning of 29 CFR 1910.20.
b. A record of TB skin test results and medical evaluations and treatment
are employee medical records within the meaning of 29 CFR 1910.20. Where
known, the workers exposure record should contain a notation of the type
of TB, to which the employee was exposed to (e.g., multidrug resistant
TB).
c. These records shall be handled according to 29 CFR 1913.10 in order
for the CSHO to determine compliance with 29 CFR 1910.20.
4. Accident prevention signs and tags: 29 CFR 1910.145.
a. In accordance with 1910.145(f)(8), a warning shall be posted outside
the Respiratory isolation or treatment room. 1910.145(f)(4) requires that
a signal word (i.e. "STOP", "HALT", or "NO ADMITTANCE") or biological hazard
symbol be presented as well as a major message (e.g., "special respiratory
isolation", "Respiratory isolation", or AFB isolation). A description of
the necessary precautions, e.g., respirators must be donned before entering.
Respiratory isolation rooms in an emergency department or a message referring
one to the nursing station for instruction must also be posted.
b. The employer shall also use biological hazard tags on air transport
components (e.g., fans, ducts, filters) which identify TB hazards to employees
associated with working on air systems that transport contaminated air
(See Appendix A, page 85).
c. The standard provides in part:
29 CFR 1910.145(e)(4): Biological hazard warning signs were not used
to signify the actual or potential presence of a biohazard and to identify
equipment, containers, rooms, materials, experimental animals, or combinations
thereof, which contain, or are contaminated with viable hazardous agents:
Sample violation language:
a. On or about [date], warning signs posted outside respiratory (Respiratory)
isolation or treatment rooms did not state the entry requirement of wearing
HEPA filtered respirators.
Abatement Note: Warning signs must be posted on respiratory isolation
or treatment rooms stating "pulmonary isolation", "respiratory isolation,"
or "AFB isolation." The sign must state specifically the precautions required
to interact with those patients. Indicators on patient records or tags
on corpses, printed in language or symbols easily recognized by employees
are additional methods to achieve this purpose.
5. OSHA 200 log - 29 CFR 1904:
a. For OSHA Form 200 record keeping purposes, both tuberculosis infections
(positive TB skin test) and tuberculosis disease are recordable in the
high risk setting referenced in section H.1. A positive skin test for tuberculosis,
even on initial testing (except pre-assignment screening) is recordable
on the OSHA 200 log because there is a presumption of work-relatedness
in these settings unless there is clear documentation that an outside exposure
occurred.
Note: In this case preassignment means the same as pre employment and
initial testing is the same as baseline testing.
b. If the employee's tuberculosis infection which was entered on the
OSHA 200 log progresses to tuberculosis disease during the five-year maintenance
period, the original entry for the infection shall be updated to reflect
the new information. Because it is difficult to determine if tuberculosis
disease resulted from the source indicated by the skin test conversion
or from subsequent exposures, only one case should be entered to avoid
double counting.
c. A positive TB skin test provided within two weeks of employment does
not have to be recorded on the OSHA 200 forms. However, the initial test
must be performed prior to any potential workplace exposure within the
initial two weeks of employment.
M. Expert Witness. The Directorate of Technical Support will
assist Regional Offices and the States in locating expert witnesses. Expert
witnesses must be contacted before issuance of citations.
1. In the event that a 5(a)(1) citation is contested, proper expert
witness support will be required. Issues which the expert must be prepared
to address include:
a. The risk to workers associated with the exposure circumstances.
b. Existence, feasibility and utility of abatement measures.
c. Recognition of the hazard in the industry.
2. Expert witnesses may also be necessary in other cases, particularly
those involving 29 CFR 1910.134.
N. Recording in the IMIS. A TB-related inspection is any health
inspection conducted to investigate the presence or alleged presence of
TB disease (i.e., a referral or complaint inspection).
1. When a TB-related inspection is conducted, complete the OSHA-1 as
for any inspection and enter the code "N 02 TB" in Item 42, Optional Information.
EXAMPLE:
Type ID Value N 2 TB
2. When an OSHA-7 is completed and the complaint alleges the presence
of TB hazards, enter the code "N 02 TB" in Item 46, Optional Information.
3. When an OSHA-90 is completed and the referral alleges the presence
of TB hazards, enter the code "N 02 TB" in Item, 26, Optional Information.
4. All IMIS case file data for TB-related inspections conducted since
October 1, 1990, shall be modified to include the appropriate TB code.
O. Referrals
1. When a complaint or inquiry is received from a source in a state
plan regarding occupational exposure to TB, the Area Office shall refer
it to the state plan designee for action.
2. When a complaint or inquiry regarding occupational exposure to TB
in a state or local government health care facility is received in a state
without an OSHA-approved state plan, the Regional Administrator shall refer
it to the appropriate State public health agency or local health agency.
P. Pre-citation Review. Citations proposed pursuant to this program
shall be reviewed prior to issuance, by the Regional Administrator and
Regional Office Solicitor for consistency with these procedures. The Directorate
of Technical Support shall be contacted to establish expert witness support.
The Office of Health Compliance Assistance shall be provided with a copy
of all citations issued related to TB during the first 6 months of this
directive.
Joseph A. Dear Assistant Secretary
Distribution: National, Regional, and Area Offices All Compliance Officers
State Designees NIOSH Regional Program Directors 7(c)(1) Consultation Project
Managers
Appendix No. A
October 28, 1994/Vol. 43/No.RR-13
MMWR Recommendations and Reports
MORBIDITY AND MORTALITY WEEKLY REPORT ----------------------------------------------------------------------------
Guidelines for preventing the Transmission of Mycobacterium Tuberculosis
in Health-Care Facilities, 1994
U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Public Health Service
Centers for Disease Control and Prevention (CDC) Atlanta, Georgia 30333
Contents
Executive Summary ...................................................1
I. Introduction ...................................................2
A. Purpose of Document .......................................2 B. Epidemiology,
Transmission, and Pathogenesis of TB ........4 C. Risk for Nosocomial Transmission
of M. tuberculosis .......5 D. Fundamentals of TB Infection Control ......................6
II. Recommendations ................................................8
A. Assignment of Responsibility ..............................8 B. Risk
Assessment, Development of the TB Infection-Control Plan, and Periodic
Reassessment .........8 1. Risk assessment ......................................8
a. General .........................................8 b. Community TB profile
...........................17 c. Case surveillance ..............................17
d. Analysis of HCW PPD test screening data ........17 e. Review of TB patient
medical records ...........18 f. Observation of TB infection-control practices
......................................19 g. Engineering evaluation .........................19
2. Development of the TB Infection-Control Plan ........19 3. Periodic
Reassessment ...............................19 4. Examples of Risk Assessment
.........................22 C. Identifying, Evaluating, and Initiating
Treatment for Patients Who May Have Active TB ......................23
1. Identifying patients who may have active TB .........23 2. Diagnostic
evaluation for active TB .................24 3. Initiation of treatment
for suspected or confirmed TB ........................................25
D. Management of Patients Who May Have Active TB in Ambulatory-Care Settings
and Emergency Departments .......25 E. Management of Hospitalized Patients
Who Have Confirmed or Suspected TB ................................27 1.
Initiation of isolation for TB ......................27
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2. TB isolation practices ..............................28 3. The TB
isolation room ...............................29 4. Discontinuation of
TB isolation .....................30 5. Discharge planning ..................................31
F. Engineering Control Recommendations ......................31 1. General
ventilation .................................31 2. Additional engineering
control approaches ...........32 a. HEPA filtration ................................32
b. UVGI ...........................................32 G. Respiratory Protection
...................................33 H. Cough-inducing and Aerosol-Generating
Procedures .........34 1. General guidelines ..................................34
2. Special considerations for bronchoscopy .............35 3. Special considerations
for the administration of aerosolized pentamidine ..........................35
I. Education and Training of HCWs ...........................36 J. HCW
Counseling, Screening, and Evaluation ................37 1. Counseling
HCWs regarding TB ........................37 2. Screening HCWs for active
TB ........................38 3. Screening HCWs for latent TB infection
..............38 4. Evaluation and management of HCWs who have positive
PPD test results or active TB ..............40 a. Evaluation .....................................40
b. Routine and follow-up chest radiographs ........40 c. Workplace restrictions
.........................41 1) Active TB .................................41
2) Latent TB infection .......................41 K. Problem Evaluation
.......................................41 1. Investigating PPD test conversions
and active TB in HCWs ..........................................42 a. Investigating
PPD test conversions in HCWs .....42 b. Investigating cases of active TB
in HCWs .......47 2. Investigating possible patient-to-patient transmission
of M. tuberculosis .....................48 3. Investigating contacts of
patients and HCWs who have infectious TB ..............................48
L. Coordination with the Public Health Department ...........49 M. Additional
Considerations for Selected Areas in Health-Care Facilities and Other Health-Care
Settings .................................................50 1. Selected
areas in health-care facilities ............50 a. Operating rooms ................................50
b. Autopsy rooms ..................................51 c. Laboratories ...................................51
2. Other health-care settings ..........................51 a. Emergency
medical services .....................51 b. Hospices .......................................52
c. Long-term care facilities ......................52 d. Correctional facilities
........................52 e. Dental settings ................................52
f. Home-health-care settings ......................53 g. Medical offices
................................54
Supplement 1: Determining the Infectiousness of a TB Patient
......57
Supplement 2: Diagnosis and Treatment of Latent TB Infection
and Active TB ......................................................59
I. Diagnostic Procedures for TB Infection and Disease .......59
A. PPD Skin Testing and Anergy Testing .................59 1. Application
and reading of PPD skin tests ......59 2. Interpretation of PPD skin tests
...............60 a. General ...................................60 b. HCWs
......................................61 3. Anergy testing .................................61
4. Pregnancy and PPD skin testing .................61 5. BCG vaccination
and PPD skin testing ...........63 6. The booster phenomenon .........................63
B. Chest Radiography ...................................64 C. Bacteriology
........................................64 II. Preventive Therapy for
Latent TB Infection and Treatment of Active TB ...................................65
A. Preventive Therapy for Latent TB Infection ..........65 B. Treatment
of Patients Who Have Active TB ............66
Supplement 3: Engineering Controls ................................69
I. Introduction .............................................69
II. Ventilation ..............................................69
A. Local Exhaust Ventilation ...........................70 1. Enclosing
devices ..............................70 2. Exterior-devices ...............................71
3. Discharge exhaust from booths, tents, and hoods ......................................71
B. General Ventilation .................................73 1. Dilution
and removal ...........................73 a. Types of general ventilation
systems ......73 b. Ventilation rates .........................74 2. Airflow
patterns within rooms (air mixing) .....74 3. Airflow direction in the
facility ..............76 a. Directional airflow .......................76
b. Negative pressure for achieving directional airflow .......................76
4. Achieving negative pressure in a room ..........76 a. Pressure differential
.....................76 b. Alternate methods for achieving negative pressure
.........................77 c. Monitoring negative pressure ..............78
C. HEPA filtration .....................................81 1. Use of HEPA
filtration when exhausting air to the outside .................................82
2. Recirculation of HEPA-filtered air to other areas of a facility ......................82
3. Recirculation of HEPA-filtered air within a room ..................................82
a. Fixed room-air recirculation systems ......84 b. Portable room-air recirculation
units .....84 c. Evaluation of room-air recirculation systems and units
.........................85 4. Installing, maintaining, and monitoring
HEPA filters ...................................85 D. TB Isolation Rooms
and Treatment Rooms ..............86 1. Preventing the escape of droplet
nuclei from the room ..................................87 2. Reducing the
concentration of droplet nuclei in the room .............................87
3. Exhaust from TB isolation rooms and treatment rooms ................................87
4. Alternatives to TB isolation rooms .............87 III. UVGI
..........................................................88 A. Applications
.............................................89 1. Duct irradiation ....................................89
2. Upper-room air irradiation ..........................89 B. Limitations
..............................................90 C. Safety Issues ............................................91
D. Exposure Criteria for UV Radiation .......................92 E. Maintenance
and Monitoring ...............................93 1. Labeling and posting
................................93 2. Maintenance .........................................94
3. Monitoring ..........................................95
Supplement 4: Respiratory Protection ..............................97
I. Considerations for Selection of Respirators ................97
A. Performance Criteria for Personal Respirators for Protection Against
Transmission of M. tuberculosis ........................................97
B. Specific Respirators ................................98 C. The Effectiveness
of Respiratory Protective Devices .............................................99
1. Face-seal leakage ..............................99 2. Filter leakage
................................100 3. Fit testing ...................................100
4. Fit checking ..................................101 5. Reuse of respirators
..........................101 II. Implementing a Personal Respiratory Protection
Program .......102
Supplement 5: Decontamination-Cleaning, Disinfecting, and Sterilizing
of Patient-Care Equipment .............................105
References ........................................................106
Glossary ..........................................................113
Index .............................................................121
List of Tables ...............................................132 List
of Figures ..............................................132
Acknowledgments
Drafts of this document have been reviewed by leaders of numerous medical,
scientific, public health, and labor organizations and others expert in
tuberculosis, acquired immunodeficiency syndrome, infection control, hospital
epidemiology, microbiology, ventilation, industrial hygiene, nursing, dental
practice, or emergency medical services. We thank the many organizations
and individuals for their thoughtful comments, suggestions, and assistance.
TB Infection-Control Guidelines Work Group
Carmine J. Bozzi Dale R. Burwen, M.D. Samuel W. Dooley, M.D. Patricia
M. Simone, M.D. National Center for Prevention Services
Consuelo Beck-Sague, M.D. Elizabeth A. Bolyard, R.N., M.P.H. William
R. Jarvis, M.D. National Center for Infectious Diseases
Philip J. Bierbaum Christine A. Hudson, M.P.H. Robert T. Hughes Linda
S. Martin, Ph.D. Robert J. Mullan, M.D. National Institute for Occupational
Safety and Health
Brian M. Willis, J.D., M.P.H. Office of the Director
Guidelines for Preventing the Transmission of Mycobacterium
tuberculosis in Health-Care Facilities, 1994
Executive Summary
This document updates and replaces all previously published guidelines
for the prevention of Mycobacterium tuberculosis transmission in health-care
facilities. The purpose of this revision is to emphasize the importance
of a) the hierarchy of control measures, including administrative and engineering
controls and personal respiratory protection; b) the use of risk assessments
for developing a written tuberculosis (TB) control plan; c) early identification
and management of persons who have TB; d) TB screening programs for health-care
workers (HCWs); e) HCW training and education; and f) the evaluation of
TB infection-control programs.
Transmission of M. tuberculosis is a recognized risk to patients and
HCWs in health-care facilities. Transmission is most likely to occur from
patients who have unrecognized pulmonary or laryngeal TB, are not on effective
anti-TB therapy, and have not been placed in TB isolation. Several recent
TB outbreaks in health-care facilities, including outbreaks of multidrug-resistant
TB, have heightened concern about nosocomial transmission. Patients who
have multidrug-resistant TB can remain infectious for prolonged periods,
which increases the risk for nosocomial and/or occupational transmission
of M. tuberculosis. Increases in the incidence of TB have been observed
in some geographic areas; these increases are related partially to the
high risk for TB among immunosuppressed persons, particularly those infected
with human immunodeficiency virus (HIV). Transmission of M. tuberculosis
to HIV-infected persons is of particular concern because these persons
are at high risk for developing active TB if they become infected with
the bacteria. Thus, health-care facilities should be particularly alert
to the need for preventing transmission of M. tuberculosis in settings
in which HIV-infected persons work or receive care.
Supervisory responsibility for the TB infection-control program should
be assigned to a designated person or group of persons who should be given
the authority to implement and enforce TB infection-control policies. An
effective TB infection-control program requires early identification, isolation,
and treatment of persons who have active TB. The primary emphasis of TB
infection-control plans in health-care facilities should be achieving these
three goals by the application of a hierarchy of control measures, including
a) the use of administrative measures to reduce the risk for exposure to
persons who have infectious TB, b) the use of engineering controls to prevent
the spread and reduce the concentration of infectious droplet nuclei, and
c) the use of personal respiratory protective equipment in areas where
there is still a risk for exposure to M. tuberculosis (e.g., TB isolation
rooms). Implementation of a TB infection-control program requires risk
assessment and development of a TB infection-control plan; early identification,
treatment, and isolation of infectious TB patients; effective engineering
controls; an appropriate respiratory protection program; HCW TB training,
education, counseling, and screening; and evaluation of the program's effectiveness.
Although completely eliminating the risk for transmission of M. tuberculosis
in all health-care facilities may not be possible at the present time,
adherence to these guidelines should reduce the risk to persons in these
settings. Recently, nosocomial TB outbreaks have demonstrated the substantial
morbidity and mortality among patients and HCWs that have been associated
with incomplete implementation of CDC's Guidelines for Preventing the Transmission
of Tuberculosis in Health-Care Facilities, with Special Focus on HIV-Related
Issues published in 1990.* Follow-up investigations at some of these hospitals
have documented that complete implementation of measures similar or identical
to those in the 1990 TB Guidelines significantly reduced or eliminated
nosocomial transmission of M. tuberculosis to patients and/or HCWs.
__________ * CDC. Guidelines for Preventing the Transmission of Tuberculosis
in Health-Care Facilities, with Special Focus on HIV-Related Issues. MMWR
1990;39(No. RR-17).
I. Introduction
A. Purpose of Document
In April 1992, the National MDR-TB Task Force published the National
Action Plan to Combat Multidrug-Resistant Tuberculosis (1). The publication
was a response to reported nosocomial outbreaks of tuberculosis (TB), including
outbreaks of multidrug-resistant TB (MDR-TB), and the increasing incidence
of TB in some geographic areas. The plan called for the update and revision
of the guidelines for preventing nosocomial transmission of Mycobacterium
tuberculosis published December 7, 1990 (2).
Public meetings were held in October 1992 and January 1993 to discuss
revision of the 1990 TB Guidelines (2). CDC received considerable input
on various aspects of infection control, including health-care worker (HCW)
education; administrative controls (e.g., having protocols for the early
identification and management of patients who have TB); the need for more
specific recommendations regarding ventilation; and clarification on the
use of respiratory protection in health-care settings. On the basis of
these events and the input received, on October 12, 1993, CDC published
in the Federal Register the Draft Guidelines For Preventing the Transmission
of Tuberculosis in Health-Care Facilities, Second Edition (3). During and
after the 90-day comment period following publication of this draft, CDC's
TB Infection-Control Guidelines Work Group received and reviewed more than
2,500 comments.
The purpose of this document is to make recommendations for reducing
the risk for transmitting M. tuberculosis to HCWs, patients, volunteers,
visitors, and other persons in these settings. The information also may
serve as a useful resource for educating HCWs about TB.
These recommendations update and replace all previously published CDC
recommendations for TB infection control in health-care facilities (2,4).
The recommendations in this document are applicable primarily to inpatient
facilities in which health care is provided (e.g., hospitals, medical wards
in correctional facilities, nursing homes, and hospices). Recommendations
applicable to ambulatory-care facilities, emergency departments, home-health-care
settings, emergency medical services, medical offices, dental settings,
and other facilities or residential settings that provide medical care
are provided in separate sections, with cross-references to other sections
of the guidelines if appropriate.
Designated personnel at health-care facilities should conduct a risk
assessment for the entire facility and for each area* and occupational
group, determine the risk for nosocomial or occupational transmission of
M. tuberculosis, and implement an appropriate TB infection-control program.
The extent of the TB infection-control program may range from a simple
program emphasizing administrative controls in settings where there is
minimal risk for exposure to M. tuberculosis, to a comprehensive program
that includes administrative controls, engineering controls, and respiratory
protection in settings where the risk for exposure is high. In all settings,
administrative measures should be used to minimize the number of HCWs exposed
to M. tuberculosis while still providing optimal care for TB patients.
HCWs providing care to patients who have TB should be informed about the
level of risk for transmission of M. tuberculosis and the appropriate control
measures to minimize that risk.
__________ * Area: a structural unit (e.g., a hospital ward or laboratory)
or functional unit (e.g., an internal medicine service) in which HCWs provide
services to and share air with a specific patient population or work with
clinical specimens that may contain viable M. tuberculosis organisms. The
risk for exposure to M. tuberculosis in a given area depends on the prevalence
of TB in the population served and the characteristics of the environment.
In this document, the term "HCWs" refers to all the paid and unpaid
persons working in health-care settings who have the potential for exposure
to M. tuberculosis. This may include, but is not limited to, physicians;
nurses; aides; dental workers; technicians; workers in laboratories and
morgues; emergency medical service (EMS) personnel; students; part-time
personnel; temporary staff not employed by the health-care facility; and
persons not involved directly in patient care but who are potentially at
risk for occupational exposure to M. tuberculosis (e.g., volunteer workers
and dietary, housekeeping, maintenance, clerical, and janitorial staff).
Although the purpose of this document is to make recommendations for
reducing the risk for transmission of M. tuberculosis in health-care facilities,
the process of implementing these recommendations must safeguard, in accordance
with applicable state and federal laws, the confidentiality and civil rights
of persons who have TB.
B. Epidemiology, Transmission, and Pathogenesis of TB
The prevalence of TB is not distributed evenly throughout all segments
of the U.S. population. Some subgroups or persons have a higher risk for
TB either because they are more likely than other persons in the general
population to have been exposed to and infected with M. tuberculosis or
because their infection is more likely to progress to active TB after they
have been infected (5). In some cases, both of these factors may be present.
Groups of persons known to have a higher prevalence of TB infection include
contacts of persons who have active TB, foreign-born persons from areas
of the world with a high prevalence of TB (e.g., Asia, Africa, the Caribbean,
and Latin America), medically underserved populations (e.g., some African-Americans,
Hispanics, Asians and Pacific Islanders, American Indians, and Alaskan
Natives), homeless persons, current or former correctional-facility inmates,
alcoholics, injecting-drug users, and the elderly. Groups with a higher
risk for progression from latent TB infection to active disease include
persons who have been infected recently (i.e., within the previous 2 years),
children less than 4 years of age, persons with fibrotic lesions on chest
radiographs, and persons with certain medical conditions (i.e., human immunodeficiency
virus [HIV] infection, silicosis, gastrectomy or jejuno-ileal bypass, being
greater than or equal to 10% below ideal body weight, chronic renal failure
with renal dialysis, diabetes mellitus, immunosuppression resulting from
receipt of high-dose corticosteroid or other immunosuppressive therapy,
and some malignancies)(5).
M. tuberculosis is carried in airborne particles, or droplet nuclei,
that can be generated when persons who have pulmonary or laryngeal TB sneeze,
cough, speak, or sing (6). The particles are an estimated 1-5 um in size,
and normal air currents can keep them airborne for prolonged time periods
and spread them throughout a room or building (7). Infection occurs when
a susceptible person inhales droplet nuclei containing M. tuberculosis,
and these droplet nuclei traverse the mouth or nasal passages, upper respiratory
tract, and bronchi to reach the alveoli of the lungs. Once in the alveoli,
the organisms are taken up by alveolar macrophages and spread throughout
the body. Usually within 2-10 weeks after initial infection with M. tuberculosis,
the immune response limits further multiplication and spread of the tubercle
bacilli; however, some of the bacilli remain dormant and viable for many
years. This condition is referred to as latent TB infection. Persons with
latent TB infection usually have positive purified protein derivative (PPD)-tuberculin
skin-test results, but they do not have symptoms of active TB, and they
are not infectious.
In general, persons who become infected with M. tuberculosis have approximately
a 10% risk for developing active TB during their lifetimes. This risk is
greatest during the first 2 years after infection. Immunocompromised persons
have a greater risk for the progression of latent TB infection to active
TB disease; HIV infection is the strongest known risk factor for this progression.
Persons with latent TB infection who become coinfected with HIV have approximately
an 8%-10% risk per year for developing active TB (8). HIV-infected persons
who are already severely immunosuppressed and who become newly infected
with M. tuberculosis have an even greater risk for developing active TB
(9-12).
The probability that a person who is exposed to M. tuberculosis will
become infected depends primarily on the concentration of infectious droplet
nuclei in the air and the duration of exposure. Characteristics of the
TB patient that enhance transmission include a) disease in the lungs, airways,
or larynx; b) presence of cough or other forceful expiratory measures;
c) presence of acid-fast bacilli (AFB) in the sputum; d) failure of the
patient to cover the mouth and nose when coughing or sneezing; e) presence
of cavitation on chest radiograph; f) inappropriate or short duration of
chemotherapy; and g) administration of procedures that can induce coughing
or cause aerosolization of M. tuberculosis (e.g., sputum induction). Environmental
factors that enhance the likelihood of transmission include a) exposure
in relatively small, enclosed spaces; b) inadequate local or general ventilation
that results in insufficient dilution and/or removal of infectious droplet
nuclei; and c) recirculation of air containing infectious droplet nuclei.
Characteristics of the persons exposed to M. tuberculosis that may affect
the risk for becoming infected are not as well defined. In general, persons
who have been infected previously with M. tuberculosis may be less susceptible
to subsequent infection. However, reinfection can occur among previously
infected persons, especially if they are severely immunocompromised. Vaccination
with Bacille of Calmette and Guerin (BCG) probably does not affect the
risk for infection; rather, it decreases the risk for progressing from
latent TB infection to active TB (13). Finally, although it is well established
that HIV infection increases the likelihood of progressing from latent
TB infection to active TB, it is unknown whether HIV infection increases
the risk for becoming infected if exposed to M. tuberculosis.
C. Risk for Nosocomial Transmission of M. tuberculosis
Transmission of M. tuberculosis is a recognized risk in health-care
facilities (14-22). The magnitude of the risk varies considerably by the
type of health-care facility, the prevalence of TB in the community, the
patient population served, the HCW's occupational group, the area of the
health-care facility in which the HCW works, and the effectiveness of TB
infection-control interventions. The risk may be higher in areas where
patients with TB are provided care before diagnosis and initiation of TB
treatment and isolation precautions (e.g., in clinic waiting areas and
emergency departments) or where diagnostic or treatment procedures that
stimulate coughing are performed. Nosocomial transmission of M. tuberculosis
has been associated with close contact with persons who have infectious
TB and with the performance of certain procedures (e.g., bronchoscopy [17],
endotracheal intubation and suctioning [18], open abscess irrigation [20],
and autopsy [21,22]). Sputum induction and aerosol treatments that induce
coughing may also increase the potential for transmission of M. tuberculosis
(23,24). Personnel of health-care facilities should be particularly alert
to the need for preventing transmission of M. tuberculosis in those facilities
in which immunocompromised persons (e.g., HIV-infected persons) work or
receive care -- especially if cough-inducing procedures, such as sputum
induction and aerosolized pentamidine treatments, are being performed.
Several TB outbreaks among persons in health-care facilities have been
reported recently (11,24-28; CDC, unpublished data). Many of these outbreaks
involved transmission of multidrug-resistant strains of M. tuberculosis
to both patients and HCWs. Most of the patients and some of the HCWs were
HIV-infected persons in whom new infection progressed rapidly to active
disease. Mortality associated with those outbreaks was high (range: 43%-93%).
Furthermore, the interval between diagnosis and death was brief (range
of median intervals: 4-16 weeks). Factors contributing to these outbreaks
included delayed diagnosis of TB, delayed recognition of drug resistance,
and delayed initiation of effective therapy -- all of which resulted in
prolonged infectiousness, delayed initiation and inadequate duration of
TB isolation, inadequate ventilation in TB isolation rooms, lapses in TB
isolation practices and inadequate precautions for cough-inducing procedures,
and lack of adequate respiratory protection. Analysis of data collected
from three of the health-care facilities involved in the outbreaks indicates
that transmission of M. tuberculosis decreased significantly or ceased
entirely in areas where measures similar to those in the 1990 TB Guidelines
were implemented (2,29-32). However, several interventions were implemented
simultaneously, and the effectiveness of the separate interventions could
not be determined.
D. Fundamentals of TB Infection Control
An effective TB infection-control program requires early identification,
isolation, and effective treatment of persons who have active TB. The primary
emphasis of the TB infection-control plan should be on achieving these
three goals. In all health-care facilities, particularly those in which
persons who are at high risk for TB work of receive care, policies and
procedures for TB control should be developed, reviewed periodically, and
evaluated for effectiveness to determine the actions necessary to minimize
the risk for transmission of M. tuberculosis.
The TB infection-control program should be based on a hierarchy of control
measures. The first level of the hierarchy, and that which affects the
largest number of persons, is using administrative measures intended primarily
to reduce the risk for exposing uninfected persons to persons who have
infectious TB. These measures include a) developing and implementing effective
written policies and protocols to ensure the rapid identification, isolation,
diagnostic evaluation, and treatment of persons likely to have TB; b) implementing
effective work practices among HCWs in the health-care facility (e.g.,
correctly wearing respiratory protection and keeping doors to isolation
rooms closed); c) educating, training, and counseling HCWs about TB; and
d) screening HCWs for TB infection and disease.
The second level of the hierarchy is the use of engineering controls
to prevent the spread and reduce the concentration of infectious droplet
nuclei. These controls include a) direct source control using local exhaust
ventilation, b) controlling direction of airflow to prevent contamination
of air in areas adjacent to the infectious source, c) diluting and removing
contaminated air via general ventilation, and d) air cleaning via air filtration
or ultraviolet germicidal irradiation (UVGI).
The first two levels of the hierarchy minimize the number of areas in
the health-care facility where exposure to infectious TB may occur, and
they reduce, but do not eliminate, the risk in those few areas where exposure
to M. tuberculosis can still occur (e.g., rooms in which patients with
known or suspected infectious TB are being isolated and treatment rooms
in which cough-inducing or aerosol-generating procedures are performed
on such patients). Because persons entering such rooms may be exposed to
M. tuberculosis, the third level of the hierarchy is the use of personal
respiratory protective equipment in these and certain other situations
in which the risk for infection with M. tuberculosis may be relatively
higher.
Specific measures to reduce the risk for transmission of M. tuberculosis
include the following:
* Assigning to specific persons in the health-care facility the supervisory
responsibility for designing, implementing, evaluating, and maintaining
the TB infection-control program (Section II.A).
* Conducting a risk assessment to evaluate the risk for transmission
of M. tuberculosis in all areas of the health-care facility, developing
a written TB infection-control program based on the risk assessment, and
periodically repeating the risk assessment to evaluate the effectiveness
of the TB infection-control program (Section II.B).
* Developing, implementing, and enforcing policies and protocols to
ensure early identification, diagnostic evaluation, and effective treatment
of patients who may have infectious TB (Section II.C; Suppl. 2).
* Providing prompt triage for and appropriate management of patients
in the outpatient setting who may have infectious TB (Section II.D).
* Promptly initiating and maintaining TB isolation for persons who may
have infectious TB and who are admitted to the inpatient setting (Section
II.E; Suppl. 1).
* Effectively planning arrangements for discharge (Section II.E).
* Developing, installing, maintaining, and evaluating ventilation and
other engineering controls to reduce the potential for airborne exposure
to M. tuberculosis (Section II.F; Suppl. 3).
* Developing, implementing, maintaining, and evaluating a respiratory
protection program (Section II.G; Suppl. 4).
* Using precautions while performing cough-inducing procedures (Section
II.H; Suppl. 3).
* Educating and training HCWs about TB, effective methods for preventing
transmission of M. tuberculosis, and the benefits of medical screening
programs (Section II.I).
* Developing and implementing a program for routine periodic counseling
and screening of HCWs for active TB and latent TB infection (Section II.J;
Suppl. 2).
* Promptly evaluating possible episodes of M. tuberculosis transmission
in health-care facilities, including PPD skin-test conversions among HCWs,
epidemiologically associated cases among HCWs or patients, and contacts
of patients or HCWs who have TB and who were not promptly identified and
isolated (Section II.K).
* Coordinating activities with the local public health department, emphasizing
reporting, and ensuring adequate discharge follow-up and the continuation
and completion of therapy (Section II.L).
II. Recommendations
A. Assignment of Responsibility
* Supervisory responsibility for the TB infection-control program should
be assigned to a designated person or group of persons with expertise in
infection control, occupational health, and engineering. These persons
should be given the authority to implement and enforce TB infection-control
policies.
* If supervisory responsibility is assigned to a committee, one person
should be designated as the TB contact person. Questions and problems can
then be addressed to this person.
B. Risk Assessment, Development of the TB Infection-Control Plan,
and Periodic Reassessment
1. Risk assessment
a. General
* TB infection-control measures for each health-care facility should
be based on a careful assessment of the risk for transmission of M. tuberculosis
in that particular setting. The first step in developing the TB infection-control
program should be to conduct a baseline risk assessment to evaluate the
risk for transmission of M. tuberculosis in each area and occupational
group in the facility (Table 1, Figure 1). Appropriate infection-control
interventions can then be developed on the basis of actual risk. Risk assessments
should be performed for all inpatient and outpatient settings (e.g., medical
and dental offices).
* Regardless of risk level, the management of patients with known or
suspected infectious TB should not vary. However, the index of suspicion
for infectious TB among patients, the frequency of HCW PPD skin testing,
the number of TB isolation rooms, and other factors will depend on whether
the risk for transmission of M. tuberculosis in the facility, area, or
occupational group is high, intermediate, low, very low, or minimal.
* The risk assessment should be conducted by a qualified person or group
of persons (e.g., hospital epidemiologists, infectious disease specialists,
pulmonary disease specialists, infection-control practitioners, health-care
administrators, occupational health personnel, engineers, HCWs, or local
public health personnel).
* The risk assessment should be conducted for the entire facility and
for specific areas within the facility (e.g., medical, TB, pulmonary, or
HIV wards; HIV, infectious disease, or pulmonary clinics; and emergency
departments or other areas where TB patients might receive care or where
cough-inducing procedures are performed). This should include both inpatient
and outpatient areas. In addition, risk assessments should be conducted
for groups of HCWs who work throughout the facility rather than in a specific
area (e.g., respiratory therapists; bronchoscopists; environmental services,
dietary, and maintenance personnel; and students, interns, residents, and
fellows).
TABLE 1. Elements of a risk assessment for tuberculosis (TB) in
health-care facilities -----------------------------------------------------------------------------
1. Review the community TB profile (from public health department data).
2. Review the number of TB patients who were treated in each area of
area of the facility (both inpatient and outpatient). (This information
can be obtained by analyzing laboratory surveillance data and by reviewing
discharge diagnoses or medical and infection-control records.)
3. Review the drug-susceptibility patterns of TB isolates of patients
who were treated at the facility.
4. Analyze purified protein derivative (PPD)-tuberculin skin-test results
of health-care workers (HCWs), by area or by occupational group for HCWs
not assigned to a specific area (e.g., respiratory therapists).
5. To evaluate infection-control parameters, review medical records
of a sample of TB patients seen at the facility.
Calculate intervals from:
* admission until TB suspected; * admission until TB evaluation performed;
* admission until acid-fast bacilli (AFB) specimens ordered; * AFB specimens
ordered until AFB specimens collected; * AFB specimens collected until
AFB smears performed and reported; * AFB specimens collected until cultures
performed and reported; * AFB specimens collected until species identification
conducted and reported; * AFB specimens collected until drug-susceptibility
tests performed and reported; * admission until TB isolation initiated;
* admission until TB treatment initiated; and * duration of TB isolation.
Obtain the following additional information:
* Were appropriate criteria used for discontinuing isolation? * Did
the patient have a history or prior admission to the facility * Was the
TB treatment regimen adequate? * Were follow-up sputum specimens collected
properly? * Was appropriate discharge planning conducted?
6. Perform an observational review of TB infection control practices.
7. Review the most recent environmental evaluation and maintenance procedures.
____________________________________________________________________________
(For Figure 1, see printed copy)
* Classification of risk for a facility, for a specific area, and for
a specific occupational group should be based on a) the profile of TB in
the community; b) the number of infectious TB patients admitted to the
area or ward, or the estimated number of infectious TB patients to whom
HCWs in an occupational group may be exposed; and c) the results of analysis
of HCW PPD test conversions (where applicable) and possible person-to-person
transmission of M. tuberculosis (Figure 1).
* All TB infection-control programs should include periodic reassessments
of risk. The frequency of repeat risk assessments should be based on the
results of the most recent risk assessment (Table 2, Figure 1).
* The "minimal-risk" category applies only to an entire facility. A
"minimal-risk" facility does not admit TB patients to inpatient or outpatient
areas and is not located in a community with TB (i.e., counties or communities
in which TB cases have not been reported during the previous year). Thus,
there is essentially no risk for exposure to TB patients in the facility.
This category may also apply to many outpatient settings (e.g., many medical
and dental offices).
(For Table 2, see printed copy)
* The "very low-risk" category generally applies only to an entire facility.
A very low-risk facility is one in which a) patients with active TB are
not admitted to inpatient areas but may receive initial assessment and
diagnostic evaluation or outpatient management in outpatient areas (e.g.,
ambulatory-care and emergency departments) and b) patients who may have
active TB and need inpatient care are promptly referred to a collaborating
facility. In such facilities, the outpatient areas in which exposure to
patients with active TB could occur should be assessed and assigned to
the appropriate low-, intermediate-, or high-risk category. Categorical
assignment will depend on the number of TB patients examined in the area
during the preceding year and whether there is evidence of nosocomial transmission
of M. tuberculosis in the area. If TB cases have been reported in the community,
but no patients with active TB have been examined in the outpatient area
during the preceding year, the area can be designated as very low risk
(e.g., many medical offices).
The referring and receiving facilities should establish a referral agreement
to prevent inappropriate management and potential loss to follow-up of
patients suspected of having TB during evaluation in the triage system
of a very low-risk facility.
In some facilities in which TB patients are admitted to inpatient areas,
a very low-risk protocol may be appropriate for areas (e.g., administrative
areas) or occupational groups that have only a very remote possibility
of exposure to M. tuberculosis.
The very low-risk category may also be appropriate for outpatient facilities
that do not provide initial assessment of persons who may have TB, but
do screen patients for active TB as part of a limited medical screening
before undertaking specialty care (e.g., dental settings).
* Low-risk" areas or occupational groups are those in which a) the PPD
test conversion rate is not greater than that for areas or groups in which
occupational exposure to M. tuberculosis is unlikely or than previous conversion
rates for the same area or group, b) no clusters* of PPD test conversions
have occurred, c) person-to-person transmission of M. tuberculosis has
not been detected, and d) fewer than six TB patients are examined or treated
per year.
__________ * Cluster: two or more PPD skin-test conversions occurring
within a 3-month period among HCWs in a specific area or occupational group,
and epidemiologic evidence suggests occupational (nosocomial) transmission.
* "Intermediate-risk" areas or occupational groups are those in which
a) the PPD test conversion rate is not greater than that for areas or groups
in which occupational exposure to M. tuberculosis is unlikely or than previous
conversion rates for the same area or group, b) no clusters of PPD test
conversions have occurred, c) person-to-person transmission of M. tuberculosis
has not been detected, and d) six or more patients with active TB are examined
or treated each year. Survey data suggest that facilities in which six
or more TB patients are examined or treated each year may have an increased
risk for transmission of M. tuberculosis (CDC, unpublished data); thus,
areas in which six or more patients with active TB are examined or treated
each year (or occupational groups in which HCWs are likely to be exposed
to six or more TB patients per year) should be classified as "intermediate
risk".
* "High-risk" areas or occupational groups are those in which a) the
PPD test conversion rate is significantly greater than for areas or groups
in which occupational exposure to M. tuberculosis is unlikely or than previous
conversion rates for the same area or group, and epidemiologic evaluation
suggests nosocomial transmission; or b) a cluster of PPD test conversions
has occurred, and epidemiologic evaluation suggests nosocomial transmission
of M. tuberculosis; or c) possible person-to-person transmission of M.
tuberculosis has been detected.
* If no data or insufficient data for adequate determination of risk
have been collected, such data should be compiled, analyzed, and reviewed
expeditiously.
b. Community TB profile
* A profile of TB in the community that is served by the facility should
be obtained from the public health department. This profile should include,
at a minimum, the incidence (and prevalence, if available) of active TB
in the community and the drug-susceptibility patterns of M. tuberculosis
isolates (i.e., the antituberculous agents to which each isolate is susceptible
and those to which it is resistant) from patients in the community.
c. Case surveillance
* Data concerning the number of suspected and confirmed active TB cases
among patients and HCWs in the facility should be systematically collected,
reviewed, and used to estimate the number of TB isolation rooms needed,
to recognize possible clusters of nosocomial transmission, and to assess
the level of potential occupational risk. The number of TB patients in
specific areas of a facility can be obtained from laboratory surveillance
data on specimens positive for AFB smears or M. tuberculosis cultures,
from infection-control records, and from databases containing information
about hospital discharge diagnoses.
* Drug-susceptibility patterns of M. tuberculosis isolates from TB patients
treated in the facility should be reviewed to identify the frequency and
patterns of drug resistance. This information may indicate a need to modify
the initial treatment regimen or may suggest possible nosocomial transmission
or increased occupational risk.
d. Analysis of HCW PPD test screening data
* Results of HCW PPD testing should be recorded in the individual HCW's
employee health record and in a retrievable aggregate database of all HCW
PPD test results. Personal identifying information should be handled confidentially.
PPD test conversion rates should be calculated at appropriate intervals
to estimate the risk for PPD test conversions for each area of the facility
and for each specific occupational group not assigned to a specific area
(Table 2). To calculate PPD test conversion rates, the total number of
previously PPD-negative HCWs tested in each area or group (i.e., the denominator)
and the number of PPD test conversions among HCWs in each area or group
(the numerator) must be obtained.
* PPD test conversion rates for each area or occupational group should
be compared with rates for areas or groups in which occupational exposure
to M. tuberculosis is unlikely and with previous conversion rates in the
same area or group to identify areas or groups where the risk for occupational
PPD test conversions may be increased. A low number of HCWs in a specific
area may result in a greatly increased rate of conversion for that area,
although the actual risk may not be significantly greater than that for
other areas. Testing for statistical significance (e.g., Fisher's exact
test or chi square test) may assist interpretation; however, lack of statistical
significance may not rule out a problem (i.e., if the number of HCWs tested
is low, there may not be adequate statistical power to detect a significant
difference). Thus, interpretation of individual situations is necessary.
* An epidemiologic investigation to evaluate the likelihood of nosocomial
transmission should be conducted if PPD test conversions are noted (Section
II.K.1).
* The frequency and comprehensiveness of the HCW PPD testing program
should be evaluated periodically to ensure that all HCWs who should be
included in the program are being tested at appropriate intervals. For
surveillance purposes, earlier detection of transmission may be enhanced
if HCWs in a given area or occupational group are tested on different scheduled
dates rather than all being tested on the same date (Section II.J.3).
e. Review of TB patient medical records
* The medical records of a sample of TB patients examined at the facility
can be reviewed periodically to evaluate infection-control parameters (Table
1). Parameters to examine may include the intervals from date of admission
until a) TB was suspected, b) specimens for AFB smears were ordered, c)
these specimens were collected, d) tests were performed, and e) results
were reported. Moreover, the adequacy of the TB treatment regimens that
were used should be evaluated.
* Medical record reviews should note previous hospital admissions of
TB patients before the onset of TB symptoms. Patient-to-patient transmission
may be suspected if active TB occurs in a patient who had a prior hospitalization
during which exposure to another TB patient occurred or if isolates from
two or more TB patients have identical characteristic drug-susceptibility
or DNA fingerprint patterns.
* Data from the case review should be used to determine if there is
a need to modify a) protocols for identifying and isolating patients who
may have infectious TB, b) laboratory procedures, c) administrative policies
and practices, or d) protocols for patient management.
f. Observation of TB infection-control practices
* Assessing adherence to the policies of the TB infection-control program
should be part of the evaluation process. This assessment should be performed
on a regular basis and whenever an increase occurs in the number of TB
patients or HCW PPD test conversions. Areas at high risk for transmission
of M. tuberculosis should be monitored more frequently than other areas.
The review of patient medical records provides information on HCW adherence
to some of the policies of the TB infection-control program. In addition,
work practices related to TB isolation (e.g., keeping doors to isolation
rooms closed) should be observed to determine if employers are enforcing,
and HCWs are adhering to, these policies and if patient adherence is being
enforced. If these policies are not being enforced or adhered to, appropriate
education and other corrective action should be implemented.
g. Engineering evaluation
* Results of engineering maintenance measures should be reviewed at
regular intervals (Table 3). Data from the most recent evaluation and from
maintenance procedures and logs should be reviewed carefully as part of
the risk assessment.
2. Development of the TB Infection-Control Plan
* Based on the results of the risk assessment, a written TB infection-control
plan should be developed and implemented for each area of the facility
and for each occupational group of HCWs not assigned to a specific area
of the facility (Table 2; Table 3).
* The occurrence of drug-resistant TB in the facility or the community,
or a relatively high prevalence of HIV infection among patients or HCWs
in the community, may increase the concern about transmission of M. tuberculosis
and may influence the decision regarding which protocol to follow (i.e.,
a higher-risk classification may be selected).
* Health-care facilities are likely to have a combination of low-, intermediate-,
and high-risk areas or occupational groups during the same time period.
The appropriate protocol should be implemented for each area or group.
* Areas in which cough-inducing procedures are performed on patients
who may have active TB should, at the minimum, implement the intermediate-risk
protocol.
3. Periodic Reassessment
* Follow-up risk assessment should be performed at the interval indicated
by the most recent risk assessment (Figure 1; Table 2). Based on the results
of the follow-up assessment, problem evaluation may need to be conducted
or the protocol may need to be modified to a higher- or lower-risk level.
TABLE 3. Characteristics of an effective tuberculosis (TB) infection-control
program*
-----------------------------------------------------------------------------
I. Assignment of responsibility
A. Assign responsibility for the TB infection-control program to qualified
person(s).
B. Ensure that persons with expertise in infection control, occupational
health, and engineering are identified and included.
II. Risk assessment, TB infection-control plan, and periodic reassessment
A. Initial risk assessment
1. Obtain information concerning TB in the community.
2. Evaluate data concerning TB patients in the facility.
3. Evaluate data concerning pruified protein derivative (PPD)-tuberculin
skin-test conversions among health-care workers (HCWs in the facility.
4. Rule out evidence of person-to-person transmission.
B. Written TB infection-control program
1. Select initial risk protocol(s).
2. Develop written TB infection-control protocols.
C. Repeat risk assessment at appropriate intervals.
1. Review current community and facility surveillance data and PPD-tuberculin
skin-test results.
2. Review records of TB patients.
3. Observe HCW infection-control practices.
4. Evaluate maintenance of engineering controls.
III. Identification, evaluation, and treatment of patients who have
TB
A. Screen patients for signs and symptoms of active TB:
1. On initial encounter in emergency department or ambulatory-care setting.
2. Before or at the time of admission.
B. Perform radiologic and bacteriologic evaluation of patients who have
signs and symptoms suggestive of TB.
C. Promptly initiate treatment.
IV. Managing outpatients who have possible infectious TB
A. Promptly initiate TB precautions.
B. Place patients in separate waiting areas or TB isolation rooms.
C. Give patients a surgical mask, a box of tissues, and instructions
regarding the use of these items.
V. Managing inpatients who have possible infectious TB
A. Promptly isolate patients who have suspected or known infectious
TB.
B. Monitor the response to treatment.
C. Follow appropriate criteria for discontinuing isolation.
VI. Engineering recommendations
A. Design local exhaust and general ventilation in collaboration with
person who have expertise in ventilation engineering.
B. Use a single-pass air systems or air recirculation after high-efficiency
particulate air (HEPA) filtration in areas where infectious TB patients
receive care.
C. Use additional measures, if needed, in areas where TB patients may
receive care.
D. Design TB isolation rooms in health-care facilities to achieve greater
than or equal to 6 air changes per hour (ACH) for existing facilities and
greater than or equal to 12 ACH for new or renovated facilities.
E. Regularly monitor and maintain engineering controls.
F. TB isolation rooms that are being used should be monitored daily
to ensure they maintain negative pressure relative to the hallways and
all surrounding areas.
G. Exhaust TB isolation room air to outside or, if absolutely unavoidable,
recirculate after HEPA filtration.
VII. Respiratory protection
A. Respiratory protective devices should meet recommended performance
criteria.
B. Respiratory protection should be used by persons entering rooms in
which patients with known or suspected infectious TB are being isolated,
by HCWs when performing cough-inducing or aerosol-generating procedures
on such patients, and by persons in other settings where administrative
and engineering controls are not likely to protect them from inhaling infectious
airborne droplet nuclei.
C. A respiratory protection program is required at all facilities in
which respiratory protection is used.
VII. Cough-inducing procedures
A. Do not perform such procedures on TB patients unless absolutely necessary.
B. Perform such procedures in areas that have local exhaust ventilation
devices (e.g., booths or special enclosures) or, if this is not feasible,
in a room that meets the ventilation requirements for TB isolation.
C. After completion of procedures, TB patients should remain in the
booth or special enclosure until their coughing subsides.
IX. HCW TB training and education
A. All HCWs should receive periodic TB education appropriate for their
work responsibilities and duties.
B. Training should include the epidemiology of TB in the facility.
C. TB education should emphasize concepts of the Pathogenesis of and
occupational risk for TB.
D. Training should describe work practices that reduce the likelihood
of transmitting M. tuberculosis.
X. HCW counseling and screening
A. Counsel all HCWs regarding TB and TB infection.
B. Counsel all HCWs about the increased risk to immunocompromised persons
for developed active TB.
C. Perform PPD skin tests on HCWs at the beginning of their employment,
and repeat PPD tests at periodic intervals.
D. Evaluate symptomatic HCWs for active TB.
XI. Evaluate HCW PPD test conversions and possible nosocomial
transmission of M. tuberculosis.
XII. Coordinate efforts with public health department(s)
-----------------------------------------------------------------------------
* A program such as this is appropriate for health-care facilities in
which there is a high risk for transmission of Mycobacterium tuberculosis.
* After each risk assessment, the staff responsible for TB control,
in conjunction with other appropriate HCWs, should review all TB control
policies to ensure that they are effective and meet current needs.
4. Examples of Risk Assessment
Examples of six hypothetical situations and the means by which surveillance
data are used to select a TB control protocol are described as follows:
Hospital A. The overall HCW PPD test conversion rate in the facility
is 1.6%. No areas or HCW occupational groups have a significantly greater
PPD test conversion rate than areas or groups in which occupational exposure
to M. tuberculosis is unlikely (or than previous rates for the same area
or group). No clusters of PPD test conversions have occurred. Patient-to-patient
transmission has not been detected. Patients who have TB are admitted to
the facility, but no area admits six or more TB patients per year. The
low-risk protocol will be followed in all areas.
Hospital B. The overall HCW PPD test conversion rate in the facility
is 1.8%. The PPD test conversion rate for the medical intensive-care unit
rate is significantly higher than all other areas in the facility. The
problem identification process is initiated (Section II.K). It is determined
that all TB patients have been isolated appropriately. Other potential
problems are then evaluated, and the cause for the higher rate is not identified.
After consulting the public health department TB infection-control program,
the high-risk protocol is followed in the unit until the PPD test conversion
rate is similar to areas of the facility in which occupational exposure
to TB patients is unlikely. If the rate remains significantly higher than
other areas, further evaluation, including environmental and procedural
studies, will be performed to identify possible reasons for the high conversion
rate.
Hospital C. The overall HCW PPD test conversion rate in the facility
is 2.4%. Rates range from 0 to 2.6% for the individual areas and occupational
groups. None of these rates is significantly higher than rates for areas
in which occupational exposure to M. tuberculosis is unlikely. No particular
HCW group has higher conversion rates than the other groups. No clusters
of HCW PPD test conversions have occurred. In two of the areas, HCWs cared
for more than six TB patients during the preceding year. These two areas
will follow the intermediate-risk protocol, and all other areas will follow
the low-risk protocol. This hospital is located in the southeastern United
States, and these conversion rates may reflect cross-reactivity with nontuberculous
mycobacteria.
Hospital D. The overall HCW PPD test conversion rate in the facility
is 1.2%. In no area did HCWs care for six or more TB patients during the
preceding year. Three of the 20 respiratory therapists tested had PPD conversions,
for a rate of 15%. The respiratory therapists who had PPD test conversions
had spent all or part of their time in the pulmonary function laboratory,
where induced sputum specimens were obtained. A low-risk protocol is maintained
for all areas and occupational groups in the facility except for respiratory
therapists. A problem evaluation is conducted in the pulmonary function
laboratory (Section II.K). It is determined that the ventilation in this
area is inadequate. Booths are installed for sputum induction. PPD testing
and the risk assessment are repeated 3 months later. If the repeat testing
at 3 months indicates that no more conversions have occurred, the respiratory
therapists will return to the low-risk protocol.
Hospital E. Hospital E is located in a community that has a relatively
low incidence of TB. To optimize TB services in the community, the four
hospitals in the community have developed an agreement that one of them
(e.g., Hospital G) will provide all inpatient services to persons who have
suspected or confirmed TB. The other hospitals have implemented protocols
in their ambulatory-care clinics and emergency departments to identify
patients who may have active TB. These patients are then transferred to
Hospital G for inpatient care if such care is considered necessary. After
discharge from Hospital G, they receive follow-up care in the public health
department's TB clinic. During the preceding year, Hospital E has identified
fewer than six TB patients in its ambulatory-care and emergency departments
and has had no PPD test conversions or other evidence of M. tuberculosis
transmission among HCWs or patients in these areas. These areas are classified
as low risk, and all other areas are classified as very low risk.
Hospital F. Hospital F is located in a county in which no TB
cases have been reported during the preceding 2 years. A risk assessment
conducted at the facility did not identify any patients who had suspected
or confirmed TB during the preceding year. The facility is classified as
minimal risk.
C. Identifying, Evaluating, and Initiating Treatment for Patients
Who May Have Active TB
The most important factors in preventing transmission of M. tuberculosis
are the early identification of patients who may have infectious TB, prompt
implementation of TB precautions for such patients, and prompt initiation
of effective treatment for those who are likely to have TB.
1. Identifying patients who may have active TB
* Health-care personnel who are assigned responsibility for TB infection
control in ambulatory-care and inpatient settings should develop, implement,
and enforce protocols for the early identification of patients who may
have infectious TB.
* The criteria used in these protocols should be based on the prevalence
and characteristics of TB in the population served by the specific facility.
These protocols should be evaluated periodically and revised according
to the results of the evaluation. Review of medical records of patients
who were examined in the facility and diagnosed as having TB may serve
as a guide for developing or revising these protocols.
* A diagnosis of TB may be considered for any patient who has a persistent
cough (i.e., a cough lasting for greater than or equal to 3 weeks) or other
signs or symptoms compatible with active TB (e.g., bloody sputum, night
sweats, weight loss, anorexia, or fever). However, the index of suspicion
for TB will vary in different geographic areas and will depend on the prevalence
of TB and other characteristics of the population served by the facility.
The index of suspicion for TB should be very high in geographic areas or
among groups of patients in which the prevalence of TB is high (Section
I.B). Appropriate diagnostic measures should be conducted and TB precautions
implemented for patients in whom active TB is suspected.
2. Diagnostic evaluation for active TB
* Diagnostic measures for identifying TB should be conducted for patients
in whom active TB is being considered. These measures include obtaining
a medical history and performing a physical examination, PPD skin test,
chest radiograph, and microscopic examination and culture of sputum or
other appropriate specimens (6,34,35). Other diagnostic procedures (e.g.,
bronchoscopy or biopsy) may be indicated for some patients (36,37).
* Prompt laboratory results are crucial to the proper treatment of the
TB patient and to early initiation of infection control. To ensure timely
results, laboratories performing mycobacteriologic tests should be proficient
at both the laboratory and administrative aspects of specimen processing.
Laboratories should use the most rapid methods available (e.g., fluorescent
microscopy for AFB smears; radiometric culture methods for isolation of
mycobacteria; p-nitro-a-acetylamino-b-hydroxy-proprophenone [NAP] test,
nucleic acid probes, or high-pressure liquid chromatography [HPLC] for
species identification; and radiometric methods for drug-susceptibility
testing). As other more rapid or sensitive tests become available, practical,
and affordable, such tests should be incorporated promptly into the mycobacteriology
laboratory. Laboratories that rarely receive specimens for mycobacteriologic
analysis should refer the specimens to a laboratory that more frequently
performs these tests.
* Results of AFB sputum smears should be available within 24 hours of
specimen collection (38).
* The probability of TB is greater among patients who have positive
PPD test results or a history of positive PPD test results, who have previously
had TB or have been exposed to M. tuberculosis, or who belong to a group
at high risk for TB (Section I.B). Active TB is strongly suggested if the
diagnostic evaluation reveals AFB in sputum, a chest radiograph suggestive
of TB, or symptoms highly suggestive of TB. TB can occur simultaneously
in immunosuppressed persons who have pulmonary infections caused by other
organisms (e.g., Pneumocystis carinii or Mycobacterium avium complex) and
should be considered in the diagnostic evaluation of all patients who have
symptoms compatible with TB (Suppl. 1; Suppl. 2).
* TB may be more difficult to diagnose among persons who have HIV infection
(or other conditions associated with severe suppression of cell-mediated
immunity) because of a nonclassical clinical or radiographic presentation
and/or the simultaneous occurrence of other pulmonary infections (e.g.,
P. carinii pneumonia and M. avium complex). The difficulty in diagnosing
TB in HIV-infected persons may be further compounded by impaired responses
to PPD skin tests (39,40), the possibly lower sensitivity of sputum smears
for detecting AFB (41), or the overgrowth of cultures with M. avium complex
in specimens from patients infected with both M. avium complex and M. tuberculosis
(42).
* Immunosuppressed patients who have pulmonary signs or symptoms that
are ascribed initially to infections or conditions other than TB should
be evaluated initially for coexisting TB. The evaluation for TB should
be repeated if the patient does not respond to appropriate therapy for
the presumed cause(s) of the pulmonary abnormalities (Suppl. 1; Suppl.
2).
* Patients with suspected or confirmed TB should be reported immediately
to the appropriate public health department so that standard procedures
for identifying and evaluating TB contacts can be initiated.
3. Initiation of treatment for suspected or confirmed TB
* Patients who have confirmed active TB or who are considered highly
likely to have active TB should be started promptly on appropriate treatment
in accordance with current guidelines (Suppl. 2)(43). In geographic areas
or facilities that have a high prevalence of MDR-TB, the initial regimen
used may need to be enhanced while the results of drug-susceptibility tests
are pending. The decision should be based on analysis of surveillance data.
* While the patient is in the health-care facility, anti-TB drugs should
be administered by directly observed therapy (DOT), the process by which
an HCW observes the patient swallowing the medications. Continuing DOT
after the patient is discharged should be strongly considered. This decision
and the arrangements for providing outpatient DOT should be made in collaboration
with the public health department.
D. Management of Patients Who May Have Active TB in Ambulatory-Care
Settings and Emergency Departments
* Triage of patients in ambulatory-care settings and emergency departments
should include vigorous efforts to promptly identify patients who have
active TB. HCWs who are the first points of contact in facilities that
serve populations at risk for TB should be trained to ask questions that
will facilitate identification of patients with signs and symptoms suggestive
of TB.
* Patients with signs or symptoms suggestive of TB should be evaluated
promptly to minimize the amount of time they are in ambulatory-care areas.
TB precautions should be followed while the diagnostic evaluation is being
conducted for these patients.
* TB precautions in the ambulatory-care setting should include a) placing
these patients in a separate area apart from other patients, and not in
open waiting areas (ideally, in a room or enclosure meeting TB isolation
requirements); b) giving these patients surgical masks* to wear and instructing
them to keep their masks on; and c) giving these patients tissues and instructing
them to cover their mouths and noses with the tissues when coughing or
sneezing.
__________ * Surgical masks are designed to prevent the respiratory
secretions of the person wearing the mask from entering the air. When not
in a TB isolation room, patients suspected of having TB should wear surgical
masks to reduce the expulsion of droplet nuclei into the air. These patients
do not need to wear particulate respirators, which are designed to filter
the air before it is inhaled by the person wearing the mask. Patients suspected
of having or known to have TB should never wear a respirator that has an
exhalation valve, because the device would provide no barrier to the expulsion
of droplet nuclei into the air.
* TB precautions should be followed for patients who are known to have
active TB and who have not completed therapy until a determination has
been made that they are noninfectious (Suppl. 1).
* Patients with active TB who need to attend a health-care clinic should
have appointments scheduled to avoid exposing HIV-infected or otherwise
severely immunocompromised persons to M. tuberculosis. This recommendation
could be accomplished by designating certain times of the day for appointments
for these patients or by treating them in areas where immunocompromised
persons are not treated.
* Ventilation in ambulatory-care areas where patients at high risk for
TB are treated should be designed and maintained to reduce the risk for
transmission of M. tuberculosis. General-use areas (e.g., waiting rooms)
and special areas (e.g., treatment or TB isolation rooms in ambulatory
areas) should be ventilated in the same manner as described for similar
inpatient areas (Sections II.E.3, II.F; Suppl. 3). Enhanced general ventilation
or the use of air-disinfection techniques (e.g., UVGI or recirculation
of air within the room through high-efficiency particulate air [HEPA] filters)
may be useful in general-use areas of facilities where many infectious
TB patients receive care (Section II.F; Suppl. 3).
* Ideally, ambulatory-care settings in which patients with TB are frequently
examined or treated should have a TB isolation room(s) available. Such
rooms are not necessary in ambulatory-care settings in which patients who
have confirmed or suspected TB are seen infrequently. However, these facilities
should have a written protocol for early identification of patients with
TB symptoms and referral to an area or a collaborating facility where the
patient can be evaluated and managed appropriately. These protocols should
be reviewed on a regular basis and revised as necessary. The additional
guidelines in Section II.H should be followed in ambulatory-care settings
where cough-inducing procedures are performed on patients who may have
active TB.
E. Management of Hospitalized Patients Who Have Confirmed or
Suspected TB
1. Initiation of isolation for TB
* In hospitals and other inpatient facilities, any patient suspected
of having or known to have infectious TB should be placed in a TB isolation
room that has currently recommended ventilation characteristics (Section
II.E.3; Suppl. 3). Written policies for initiating isolation should specify
a) the indications for isolation, b) the person(s) authorized to initiate
and discontinue isolation, c) the isolation practices to follow, d) the
monitoring of isolation, e) the management of patients who do not adhere
to isolation practices, and f) the criteria for discontinuing isolation.
* In rare circumstances, placing more than one TB patient together in
the same room may be acceptable. This practice is sometimes referred to
as "cohorting" Because of the risk for patients becoming superinfected
with drug-resistant organisms, patients with TB should be placed in the
same room only if all patients involved a) have culture-confirmed TB, b)
have drug-susceptibility test results available on a current specimen obtained
during the present hospitalization, c) have identical drug-susceptibility
patterns on these specimens, and d) are on effective therapy. Having isolates
with identical DNA fingerprint patterns is not adequate evidence for placing
two TB patients together in the same room, because isolates with the same
DNA fingerprint pattern can have different drug-susceptibility patterns.
* Pediatric patients with suspected or confirmed TB should be evaluated
for potential infectiousness according to the same criteria as are adults
(i.e., on the basis of symptoms, sputum AFB smears, radiologic findings,
and other criteria) (Suppl. 1). Children who may be infectious should be
placed in isolation until they are determined to be noninfectious. Pediatric
patients who may be infectious include those who have laryngeal or extensive
pulmonary involvement, pronounced cough, positive sputum AFB smears, or
cavitary TB or those for whom cough-inducing procedures are performed (44).
* The source of infection for a child with TB is often a member of the
child's family (45). Therefore, parents and other visitors of all pediatric
TB patients should be evaluated for TB as soon as possible. Until they
have been evaluated, or the source case is identified, they should wear
surgical masks when in areas of the facility outside of the child's room,
and they should refrain from visiting common areas in the facility (e.g.,
the cafeteria or lounge areas).
* TB patients in intensive-care units should be treated the same as
patients in noncritical-care settings. They should be placed in TB isolation
and have respiratory secretions submitted for AFB smear and culture if
they have undiagnosed pulmonary symptoms suggestive of TB.
* If readmitted to a health-care facility, patients who are known to
have active TB and who have not completed therapy should have TB precautions
applied until a determination has been made that they are noninfectious
(Suppl. 1).
2. TB isolation practices
* Patients who are placed in TB isolation should be educated about the
mechanisms of M. tuberculosis transmission and the reasons for their being
placed in isolation. They should be taught to cover their mouths and noses
with a tissue when coughing or sneezing, even while in the isolation room,
to contain liquid drops and droplets before they are expelled into the
air (46).
* Efforts should be made to facilitate patient adherence to isolation
measures (e.g., staying in the TB isolation room). Such efforts might include
the use of incentives (e.g., providing them with telephones, televisions,
or radios in their rooms or allowing special dietary requests). Efforts
should also be made to address other problems that could interfere with
adherence to isolation (e.g., management of the patient's withdrawal from
addictive substances [including tobacco]).
* Patients placed in isolation should remain in their isolation rooms
with the door closed. If possible, diagnostic and treatment procedures
should be performed in the isolation rooms to avoid transporting patients
through other areas of the facility. If patients who may have infectious
TB must be transported outside their isolation rooms for medically essential
procedures that cannot be performed in the isolation rooms, they should
wear surgical masks that cover their mouths and noses during transport.
Persons transporting the patients do not need to wear respiratory protection
outside the TB isolation rooms. Procedures for these patients should be
scheduled at times when they can be performed rapidly and when waiting
areas are less crowded.
* Treatment and procedure rooms in which patients who have infectious
TB or who have an undiagnosed pulmonary disease and are at high risk for
active TB receive care should meet the ventilation recommendations for
isolation rooms (Section II.E.3; Suppl. 3). Ideally, facilities in which
TB patients are frequently treated should have an area in the radiology
department that is ventilated separately for TB patients. If this is not
possible, TB patients should wear surgical masks and should stay in the
radiology suite the minimum amount of time possible, then be returned promptly
to their isolation rooms.
* The number of persons entering an isolation room should be minimal.
All persons who enter an isolation room should wear respiratory protection
(Section II.G; Suppl. 4). The patient's visitors should be given respirators
to wear while in the isolation room, and they should be given general instructions
on how to use their respirators.
* Disposable items contaminated with respiratory secretions are not
associated with transmission of M. tuberculosis. However, for general infection-control
purposes, these items should be handled and transported in a manner that
reduces the risk for transmitting other microorganisms to patients, HCWs,
and visitors and that decreases environmental contamination in the health-care
facility. Such items should be disposed of in accordance with hospital
policy and applicable regulations (Suppl. 5).
3. The TB isolation room
* TB isolation rooms should be single-patient rooms with special ventilation
characteristics appropriate for the purposes of isolation (Suppl. 3). The
primary purposes of TB isolation rooms are to a) separate patients who
are likely to have infectious TB from other persons; b) provide an environment
that will allow reduction of the concentration of droplet nuclei through
various engineering methods; and c) prevent the escape of droplet nuclei
from the TB isolation room and treatment room, thus preventing entry of
M. tuberculosis into the corridor and other areas of the facility.
* To prevent the escape of droplet nuclei, the TB isolation room should
be maintained under negative pressure (Suppl. 3). Doors to isolation rooms
should be kept closed, except when patients or personnel must enter or
exit the room, so that negative pressure can be maintained.
* Negative pressure in the room should be monitored daily while the
room is being used for TB isolation.
* The American Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc. (ASHRAE) (47), the American Institute of Architects (AIA)
(48), and the Health Resources and Services Administration (49) recommend
a minimum of 6 air changes per hour (ACH) for TB isolation and treatment
rooms. This ventilation rate is based on comfort and odor control considerations.
The effectiveness of this level of airflow in reducing the concentration
of droplet nuclei in the room, thus reducing the transmission of airborne
pathogens, has not been evaluated directly or adequately.
Ventilation rates of greater than 6 ACH are likely to produce an incrementally
greater reduction in the concentration of bacteria in a room than are lower
rates (50-52). However, accurate quantitation of decreases in risk that
would result from specific increases in general ventilation levels has
not been performed and may not be possible.
For the purposes of reducing the concentration of droplet nuclei, TB
isolation and treatment rooms in existing health-care facilities should
have an airflow of greater than or equal to 6 ACH. Where feasible, this
airflow rate should be increased to greater than or equal to 12 ACH by
adjusting or modifying the ventilation system or by using auxiliary means
(e.g., recirculation of air through fixed HEPA filtration systems or portable
air cleaners) (Suppl. 3, Section II.B.5.a) (53). New construction or renovation
of existing health-care facilities should be designed so that TB isolation
rooms achieve an airflow of greater than or equal to 12 ACH.
* Air from TB isolation rooms and treatment rooms used to treat patients
who have known or suspected infectious TB should be exhausted to the outside
in accordance with applicable federal, state, and local regulations. The
air should not be recirculated into the general ventilation. In some instances,
recirculation of air into the general ventilation system from such rooms
is unavoidable (i.e., in existing facilities in which the ventilation system
or facility configuration makes venting the exhaust to the outside impossible).
In such cases, HEPA filters should be installed in the exhaust duct leading
from the room to the general ventilation system to remove infectious organisms
and particulates the size of droplet nuclei from the air before it is returned
to the general ventilation system (Section II.F; Suppl. 3). Air from TB
isolation and treatment rooms in new or renovated facilities should not
be recirculated into the general ventilation system.
* Although not required, an anteroom may increase the effectiveness
of the isolation room by minimizing the potential escape of droplet nuclei
into the corridor when the door is opened. To work effectively, the anteroom
should have positive air pressure in relation to the isolation room. The
pressure relationship between the anteroom and the corridor may vary according
to ventilation design.
* Upper-room air UVGI may be used as an adjunct to general ventilation
in the isolation room (Section II.F; Suppl. 3). Air in the isolation room
may be recirculated within the room through HEPA filters or UVGI devices
to increase the effective ACH and to increase thermal efficiency.
* Health-care facilities should have enough isolation rooms to appropriately
isolate all patients who have suspected or confirmed active TB. This number
should be estimated using the results of the risk assessment of the health-care
facility. Except for minimal- and very low-risk health-care facilities,
all acute-care inpatient facilities should have at least one TB isolation
room (Section II.B).
* Grouping isolation rooms together in one area of the facility may
reduce the possibility of transmitting M. tuberculosis to other patients
and may facilitate care of TB patients and the installation and maintenance
of optimal engineering (particularly ventilation) controls.
4. Discontinuation of TB isolation
* TB isolation can be discontinued if the diagnosis of TB is ruled out.
For some patients, TB can be ruled out when another diagnosis is confirmed.
If a diagnosis of TB cannot be ruled out, the patient should remain in
isolation until a determination has been made that the patient is noninfectious.
However, patients can be discharged from the healthcare facility while
still potentially infectious if appropriate postdischarge arrangements
can be ensured (Section II.E.5).
* The length of time required for a TB patient to become noninfectious
after starting anti-TB therapy varies considerably (Suppl. 1). Isolation
should be discontinued only when the patient is on effective therapy, is
improving clinically, and has had three consecutive negative sputum AFB
smears collected on different days.
* Hospitalized patients who have active TB should be monitored for relapse
by having sputum AFB smears examined regularly (e.g., every 2 weeks). Nonadherence
to therapy (i.e., failure to take medications as prescribed) and the presence
of drug-resistant organisms are the two most common reasons why patients
remain infectious despite treatment. These reasons should be considered
if a patient does not respond clinically to therapy within 2-3 weeks.
* Continued isolation throughout the hospitalization should be strongly
considered for patients who have MDR-TB because of the tendency for treatment
failure or relapse (i.e., difficulty in maintaining noninfectiousness)
that has been observed in such cases.
5. Discharge planning
* Before a TB patient is discharged from the health-care facility, the
facility's staff and public health authorities should collaborate to ensure
continuation of therapy. Discharge planning in the health-care facility
should include, at a minimum, a) a confirmed outpatient appointment with
the provider who will manage the patient until the patient is cured, b)
sufficient medication to take until the outpatient appointment, and c)
placement into case management (e.g., DOT) or outreach programs of the
public health department. These plans should be initiated and in place
before the patient's discharge.
* Patients who may be infectious at the time of discharge should only
be discharged to facilities that have isolation capability or to their
homes. Plans for discharging a patient who will return home must consider
whether all the household members were infected previously and whether
any uninfected household members are at very high risk for active TB if
infected (e.g., children less than 4 years of age or persons infected with
HIV or otherwise severely immunocompromised). If the household does include
such persons, arrangements should be made to prevent them from being exposed
to the TB patient until a determination has been made that the patient
is noninfectious.
F. Engineering Control Recommendations
1. General ventilation
This section deals only with engineering controls for general-use areas
of health-care facilities (e.g., waiting-room areas and emergency departments).
Recommendations for engineering controls for specific areas of the facility
(e.g., TB isolation rooms) are contained in the sections encompassing those
areas. Details regarding ventilation design, evaluation, and supplemental
approaches are described in Supplement 3.
* Health-care facilities should either a) include as part of their staff
an engineer or other professional with expertise in ventilation or b) have
this expertise available from a consultant who is an expert in ventilation
engineering and who also has hospital experience. These persons should
work closely with infection-control staff to assist in controlling airborne
infections.
* Ventilation system designs in health-care facilities should meet any
applicable federal, state, and local requirements.
* The direction of airflow in health-care facilities should be designed,
constructed, and maintained so that air flows from clean areas to less-clean
areas.
* Health-care facilities serving populations that have a high prevalence
of TB may need to supplement the general ventilation or use additional
engineering approaches (i.e., HEPA filtration or UVGI) in general-use areas
where TB patients are likely to go (e.g., waiting-room areas, emergency
departments, and radiology suites). A single-pass, nonrecirculating system
that exhausts air to the outside, a recirculation system that passes air
through HEPA filters before recirculating it to the general ventilation
system, or upper air UVGI may be used in such areas.
2. Additional engineering control approaches
a. HEPA filtration
HEPA filters may be used in a number of ways to reduce or eliminate
infectious droplet nuclei from room air or exhaust (Suppl. 3). These methods
include placement of HEPA filters a) in exhaust ducts discharging air from
booths or enclosures into the surrounding room; b) in ducts or in ceiling-
or wall-mounted units, for recirculation of air within an individual room
(fixed recirculation systems); c) in portable air cleaners; d) in exhaust
ducts to remove droplet nuclei from air being discharged to the outside,
either directly or through ventilation equipment; and e) in ducts discharging
air from the TB isolation room into the general ventilation system. In
any application, HEPA filters should be installed carefully and maintained
meticulously to ensure adequate functioning.
The manufacturers of in-room air cleaning equipment should provide documentation
of the HEPA filter efficiency and the efficiency of the device in lowering
room air contaminant levels.
b. UVGI
For general-use areas in which the risk for transmission of M. tuberculosis
is relatively high, UVGI lamps may be used as an adjunct to ventilation
for reducing the concentration of infectious droplet nuclei (Suppl. 3),
although the effectiveness of such units has not been evaluated adequately.
Ultra-violet (UV) units can be installed in a room or corridor to irradiate
the air in the upper portion of the room (i.e., upper-room air irradiation),
or they can be installed in ducts to irradiate air passing through the
ducts. UV units installed in ducts should not be substituted for HEPA filters
in ducts that discharge air from TB isolation rooms into the general ventilation
system. However, UV units can be used in ducts that recirculate air back
into the same room.
To function properly and decrease hazards to HCWs and others in the
health-care facility, UV lamps should be installed properly and maintained
adequately, which includes the monitoring of irradiance levels. UV tubes
should be changed according to the manufacturer's instructions or when
meter readings indicate tube failure. An employee trained in the use and
handling of UV lamps should be responsible for these measures and for keeping
maintenance records. Applicable safety guidelines should be followed. Caution
should be exercised to protect HCWs, patients, visitors, and others from
excessive exposure to UV radiation.
G. Respiratory Protection
* Personal respiratory protection should be used by a) persons entering
rooms in which patients with known or suspected infectious TB are being
isolated, b) persons present during cough-inducing or aerosol-generating
procedures performed on such patients, and c) persons in other settings
where administrative and engineering controls are not likely to protect
them from inhaling infectious airborne droplet nuclei (Suppl. 4). These
other settings include transporting patients who may have infectious TB
in emergency transport vehicles and providing urgent surgical or dental
care to patients who may have infectious TB before a determination has
been made that the patient is noninfectious (Suppl. 1).
* Respiratory protective devices used in health-care settings for protection
against M. tuberculosis should meet the following standard performance
criteria:
1. The ability to filter particles 1 um in size in the unloaded* state
with a filter efficiency of greater than or equal to 95% (i.e., filter
leakage of less than or equal to 5%), given flow rates of up to 50 L per
minute.
__________ * Some filters become more efficient as they become loaded
with dust. Health-care settings do not have enough dust in the air to load
a filter on a respirator. Therefore, the filter efficiency for respirators
used in health-care settings must be determined in the unloaded state.
2. The ability to be qualitatively or quantitatively fit tested in a
reliable way to obtain a face-seal leakage of less than or equal to 10%
(54,55).
3. The ability to fit the different facial sizes and characteristics
of HCWs, which can usually be met by making the respirators available in
at least three sizes.
4. The ability to be checked for facepiece fit, in accordance with standards
established by the Occupational Safety and Health Administration (OSHA)
and good industrial hygiene practice, by HCWs each time they put on their
respirators (54,55).
* The facility's risk assessment may identify a limited number of selected
settings (e.g., bronchoscopy performed on patients suspected of having
TB or autopsy performed on deceased persons suspected of having had active
TB at the time of death) where the estimated risk for transmission of M.
tuberculosis may be such that a level of respiratory protection exceeding
the standard performance criteria is appropriate. In such circumstances,
a level of respiratory protection exceeding the standard criteria and compatible
with patient-care delivery (e.g., more protective negative-pressure respirators;
powered air-purifying particulate respirators [PAPRs]; or positive-pressure
air-line, half-mask respirators) should be provided by employers to HCWs
who are exposed to M. tuberculosis. Information on these and other respirators
is in the NIOSH Guide to Industrial Respiratory Protection (55) and in
Supplement 4 of this document.
* In some settings, HCWs may be at risk for two types of exposure: a)
inhalation of M. tuberculosis and b) mucous membrane exposure to fluids
that may contain bloodborne pathogens. In these settings, protection against
both types of exposure should be used.
* When operative procedures (or other procedures requiring a sterile
field) are performed on patients who may have infectious TB, respiratory
protection worn by the HCW should serve two functions: a) it should protect
the surgical field from the respiratory secretions of the HCW, and b) it
should protect the HCW from infectious droplet nuclei that may be expelled
by the patient or generated by the procedure. Respirators with exhalation
valves and most positive-pressure respirators do not protect the sterile
field.
* Health-care facilities in which respiratory protection is used to
prevent inhalation of M. tuberculosis are required by OSHA to develop,
implement, and maintain a respiratory protection program (Suppl. 4). All
HCWs who use respiratory protection should be included in this program.
Visitors to TB patients should be given respirators to wear while in isolation
rooms, and they should be given general instructions on how to use their
respirators.
* Facilities that do not have isolation rooms and do not perform cough-inducing
procedures on patients who may have TB may not need to have a respiratory
protection program for TB. However, such facilities should have written
protocols for the early identification of patients who have signs or symptoms
of TB and procedures for referring these patients to a facility where they
can be evaluated and managed appropriately. These protocols should be evaluated
regularly and revised as needed.
* Surgical masks are designed to prevent the respiratory secretions
of the person wearing the mask from entering the air. To reduce the expulsion
of droplet nuclei into the air, patients suspected of having TB should
wear surgical masks when not in TB isolation rooms. These patients do not
need to wear particulate respirators, which are designed to filter the
air before it is inhaled by the person wearing the respirator. Patients
suspected of having or known to have TB should never wear a respirator
that has an exhalation valve, because this type of respirator does not
prevent expulsion of droplet nuclei into the air.
H. Cough-Inducing and Aerosol-Generating Procedures
1. General guidelines
Procedures that involve instrumentation of the lower respiratory tract
or induce coughing can increase the likelihood of droplet nuclei being
expelled into the air. These cough-inducing procedures include endotracheal
intubation and suctioning, diagnostic sputum induction, aerosol treatments
(e.g., pentamidine therapy), and bronchoscopy. Other procedures that can
generate aerosols (e.g., irrigation of tuberculous abscesses, homogenizing
or lyophilizing tissue, or other processing of tissue that may contain
tubercle bacilli) are also covered by these recommendations.
* Cough-inducing procedures should not be performed on patients who
may have infectious TB unless the procedures are absolutely necessary and
can be performed with appropriate precautions.
* All cough-inducing procedures performed on patients who may have infectious
TB should be performed using local exhaust ventilation devices (e.g., booths
or special enclosures) or, if this is not feasible, in a room that meets
the ventilation requirements for TB isolation.
* HCWs should wear respiratory protection when present in rooms or enclosures
in which cough-inducing procedures are being performed on patients who
may have infectious TB.
* After completion of cough-inducing procedures, patients who may have
infectious TB should remain in their isolation rooms or enclosures and
not return to common waiting areas until coughing subsides. They should
be given tissues and instructed to cover their mouths and noses with the
tissues when coughing. If TB patients must recover from sedatives or anesthesia
after a procedure (e.g, after a bronchoscopy), they should be placed in
separate isolation rooms (and not in recovery rooms with other patients)
while they are being monitored.
* Before the booth, enclosure, or room is used for another patient,
enough time should be allowed to pass for at least 99% of airborne contaminants
to be removed. This time will vary according to the efficiency of the ventilation
or filtration used (Suppl. 3, Table S-31).
2. Special considerations for bronchoscopy
* If performing bronchoscopy in positive-pressure rooms (e.g., operating
rooms) is unavoidable, TB should be ruled out as a diagnosis before the
procedure is performed. If the bronchoscopy is being performed for the
purpose of diagnosing pulmonary disease and that diagnosis could include
TB, the procedure should be performed in a room that meets TB isolation
ventilation requirements.
3. Special considerations for the administration of aerosolized
pentamidine
* Patients should be screened for active TB before prophylactic therapy
with aerosolized pentamidine is initiated. Screening should include obtaining
a medical history and performing skin testing and chest radiography.
* Before each subsequent treatment with aerosolized pentamidine, patients
should be screened for symptoms suggestive of TB (e.g., development of
a productive cough). If such symptoms are elicited, a diagnostic evaluation
for TB should be initiated.
* Patients who have suspected or confirmed active TB should take, if
clinically practical, oral prophylaxis for P. carinii pneumonia.
I. Education and Training of HCWs
All HCWs, including physicians, should receive education regarding TB
that is relevant to persons in their particular occupational group. Ideally,
training should be conducted before initial assignment, and the need for
additional training should be reevaluated periodically (e.g., once a year).
The level and detail of this education will vary according to the HCW's
work responsibilities and the level of risk in the facility (or area of
the facility) in which the HCW works. However, the program may include
the following elements:
* The basic concepts of M. tuberculosis transmission, pathogenesis,
and diagnosis, including information concerning the difference between
latent TB infection and active TB disease, the signs and symptoms of TB,
and the possibility of reinfection.
* The potential for occupational exposure to persons who have infectious
TB in the health-care facility, including information concerning the prevalence
of TB in the community and facility, the ability of the facility to properly
isolate patients who have active TB, and situations with increased risk
for exposure to M. tuberculosis.
* The principles and practices of infection control that reduce the
risk for transmission of M. tuberculosis, including information concerning
the hierarchy of TB infection-control measures and the written policies
and procedures of the facility. Site-specific control measures should be
provided to HCWs working in areas that require control measures in addition
to those of the basic TB infection-control program.
* The purpose of PPD skin testing, the significance of a positive PPD
test result, and the importance of participating in the skin-test program.
* The principles of preventive therapy for latent TB infection. These
principles include the indications, use, effectiveness, and the potential
adverse effects of the drugs (Suppl. 2).
* The HCW's responsibility to seek prompt medical evaluation if a PPD
test conversion occurs or if symptoms develop that could be caused by TB.
Medical evaluation will enable HCWs who have TB to receive appropriate
therapy and will help to prevent transmission of M. tuberculosis to patients
and other HCWs.
* The principles of drug therapy for active TB.
* The importance of notifying the facility if the HCW is diagnosed with
active TB so that contact investigation procedures can be initiated.
* The responsibilities of the facility to maintain the confidentiality
of the HCW while ensuring that the HCW who has TB receives appropriate
therapy and is noninfectious before returning to duty.
* The higher risks associated with TB infection in persons who have
HIV infection or other causes of severely impaired cell-mediated immunity,
including a) the more frequent and rapid development of clinical TB after
infection with M. tuberculosis, b) the differences in the clinical presentation
of disease, and c) the high mortality rate associated with MDR-TB in such
persons.
* The potential development of cutaneous anergy as immune function (as
measured by CD4+ T-lymphocyte counts) declines.
* Information regarding the efficacy and safety of BCG vaccination and
the principles of PPD screening among BCG recipients.
* The facility's policy on voluntary work reassignment options for immunocompromised
HCWs.
J. HCW Counseling, Screening, and Evaluation
* A TB counseling, screening, and prevention program for HCWs should
be established to protect both HCWs and patients. HCWs who have positive
PPD test results, PPD test conversions, or symptoms suggestive of TB should
be identified, evaluated to rule out a diagnosis of active TB, and started
on therapy or preventive therapy if indicated (5). In addition, the results
of the HCW PPD screening program will contribute to evaluation of the effectiveness
of current infection-control practices.
1. Counseling HCWs regarding TB
* Because of the increased risk for rapid progression from latent TB
infection to active TB in HIV-infected or otherwise severely immunocompromised
persons, all HCWs should know if they have a medical condition or are receiving
a medical treatment that may lead to severely impaired cell-mediated immunity.
HCWs who may be at risk for HIV infection should know their HIV status
(i.e., they should be encouraged to voluntarily seek counseling and testing
for HIV antibody status). Existing guidelines for counseling and testing
should be followed routinely (56). Knowledge of these conditions allows
the HCW to seek the appropriate preventive measures outlined in this document
and to consider voluntary work reassignments. Of particular importance
is that HCWs need to know their HIV status if they are at risk for HIV
infection and they work in settings where patients who have drug-resistant
TB may be encountered.
* All HCWs should be informed about the need to follow existing recommendations
for infection control to minimize the risk for exposure to infectious agents;
implementation of these recommendations will greatly reduce the risk for
occupational infections among HCWs (57). All HCWs should also be informed
about the potential risks to severely immunocompromised persons associated
with caring for patients who have some infectious diseases, including TB.
It should be emphasized that limiting exposure to TB patients is the most
protective measure that severely immunosuppressed HCWs can take to avoid
becoming infected with M. tuberculosis. HCWs who have severely impaired
cell-mediated immunity and who may be exposed to M. tuberculosis may consider
a change in job setting to avoid such exposure. HCWs should be advised
of the option that severely immunocompromised HCWs can choose to transfer
voluntarily to areas and work activities in which there is the lowest possible
risk for exposure to M. tuberculosis. This choice should be a personal
decision for HCWs after they have been informed of the risks to their health.
* Employers should make reasonable accommodations (e.g., alternative
job assignments) for employees who have a health condition that compromises
cell-mediated immunity and who work in settings where they may be exposed
to M. tuberculosis. HCWs who are known to be immunocompromised should be
referred to employee health professionals who can individually counsel
the employees regarding their risk for TB. Upon the request of the immunocompromised
HCW, employers should offer, but not compel, a work setting in which the
HCW would have the lowest possible risk for occupational exposure to M.
tuberculosis. Evaluation of these situations should also include consideration
of the provisions of the Americans With Disabilities Act of 1990* and other
applicable federal, state, and local laws. __________ * Americans With
Disabilities Act of 1990. PL 101-336, 42 U.S.C. 12101 et seq.
* All HCWs should be informed that immunosuppressed HCWs should have
appropriate follow-up and screening for infectious diseases, including
TB, provided by their medical practitioner. HCWs who are known to be HIV-infected
or otherwise severely immunosuppressed should be tested for cutaneous anergy
at the time of PPD testing (Suppl. 2). Consideration should be given to
retesting, at least every 6 months, those immunocompromised HCWs who are
potentially exposed to M. tuberculosis because of the high risk for rapid
progression to active TB if they become infected.
* Information provided by HCWs regarding their immune status should
be treated confidentially. If the HCW requests voluntary job reassignment,
the confidentiality of the HCW should be maintained. Facilities should
have written procedures on confidential handling of such information.
2. Screening HCWs for active TB
* Any HCW who has a persistent cough (i.e., a cough lasting greater
than or equal to 3 weeks), especially in the presence of other signs or
symptoms compatible with active TB (e.g., weight loss, night sweats, bloody
sputum, anorexia, or fever), should be evaluated promptly for TB. The HCW
should not return to the workplace until a diagnosis of TB has been excluded
or until the HCW is on therapy and a determination has been made that the
HCW is noninfectious.
3. Screening HCWs for latent TB infection
* The risk assessment should identify which HCWs have potential for
exposure to M. tuberculosis and the frequency with which the exposure may
occur. This information is used to determine which HCWs to include in the
skin-testing program and the frequency with which they should be Table
2).
* If HCWs are from risks groups with increased prevalence of TB, consideration
may be given to including them in the skin-testing program, even if they
do not have potential occupational exposure to M. tuberculosis, so that
converters can be identified and preventive therapy offered.
* Administrators of health-care facilities should ensure that physicians
and other personnel not paid by, but working in, the facility receive skin
testing at appropriate intervals for their occupational group and work
location.
* During the pre-employment physical or when applying for hospital privileges,
HCWs who have potential for exposure to M. tuberculosis (Table 2), including
those with a history of BCG vaccination, should have baseline PPD skin
testing performed (Suppl. 2). For HCWs who have not had a documented negative
PPD test result during the preceding 12 months, the baseline PPD testing
should employ the two-step method; this will detect boosting phenomena
that might be misinterpreted as a skin-test conversion. Decisions concerning
the use of the two-step procedure for baseline testing in a particular
facility should be based on the frequency of boosting in that facility.
* HCWs who have a documented history of a positive PPD test, adequate
treatment for disease, or adequate preventive therapy for infection, should
be exempt from further PPD screening unless they develop signs or symptoms
suggestive of TB.
* PPD-negative HCWs should undergo repeat PPD testing at regular intervals
as determined by the risk assessment (Section II.B). In addition, these
HCWs should be tested whenever they have been exposed to a TB patient and
appropriate precautions were not observed at the time of exposure (Section
II.K.3). Performing PPD testing of HCWs who work in the same area or occupational
group on different scheduled dates (e.g., test them on their birthdays
or on their employment anniversary dates), rather than testing all HCWs
in the area or group on the same day, may lead to earlier detection of
M. tuberculosis transmission.
* All PPD tests should be administered, read, and interpreted in accordance
with current guidelines by specified trained personnel (Suppl. 2). At the
time their test results are read, HCWs should be informed about the interpretation
of both positive and negative PPD test results. This information should
indicate that the interpretation of an induration that is 5-9 mm in diameter
depends on the HCW's immune status and history of exposure to persons who
have infectious TB. Specifically, HCWs who have indurations of 5-9 mm in
diameter should be advised that such results may be considered positive
for HCWs who are contacts of persons with infectious TB or who have HIV
infection or other causes of severe immunosuppression (e.g., immunosuppressive
therapy for organ transplantation).
* When an HCW who is not assigned regularly to a single work area has
a PPD test conversion, appropriate personnel should identify the areas
where the HCW worked during the time when infection was likely to have
occurred. This information can then be considered in analyzing the risk
for transmission in those areas.
* In any area of the facility where transmission of M. tuberculosis
is known to have occurred, a problem evaluation should be conducted (Section
II.K), and the frequency of skin testing should be determined according
to the applicable risk category (Section II.B).
* PPD test results should be recorded confidentially in the individual
HCW's employee health record and in an aggregate database of all HCW PPD
test results. The database can be analyzed periodically to estimate the
risk for acquiring new infection in specific areas or occupational groups
in the facility.
4. Evaluation and management of HCWs who have positive PPD test
results or active TB
a. Evaluation
* All HCWs with newly recognized positive PPD test results or PPD test
conversions should be evaluated promptly for active TB. This evaluation
should include a clinical examination and a chest radiograph. If the history,
clinical examination, or chest radiograph is compatible with active TB,
additional tests should be performed (Section II.C.2). If symptoms compatible
with TB are present, the HCW should be excluded from the workplace until
either a) a diagnosis of active TB is ruled out or b) a diagnosis of active
TB was established, the HCW is being treated, and a determination has been
made that the HCW is noninfectious (Suppl. 2). HCWs who do not have active
TB should be evaluated for preventive therapy according to published guidelines
(Suppl. 2).
* If an HCW's PPD test result converts to positive, a history of confirmed
or suspected TB exposure should be obtained in an attempt to determine
the potential source. When the source of exposure is known, the drug-susceptibility
pattern of the M. tuberculosis isolated from the source should be identified
so that the correct curative or preventive therapy can be initiated for
the HCW with the PPD test conversion. The drug-susceptibility pattern should
be recorded in the HCW's medical record, where it will be available if
the HCW subsequently develops active TB and needs therapy specific for
the drug-susceptibility pattern.
* All HCWs, including those with histories of positive PPD test results,
should be reminded periodically about the symptoms of TB and the need for
prompt evaluation of any pulmonary symptoms suggestive of TB.
b. Routine and follow-up chest radiographs
* Routine chest radiographs are not required for asymptomatic, PPD-negative
HCWs. HCWs with positive PPD test results should have a chest radiograph
as part of the initial evaluation of their PPD test; if negative, repeat
chest radiographs are not needed unless symptoms develop that could be
attributed to TB (58). However, more frequent monitoring for symptoms of
TB may be considered for recent converters and other PPD-positive HCWs
who are at increased risk for developing active TB (e.g., HIV-infected
or otherwise severely immunocompromised HCWs).
c. Workplace restrictions
1) Active TB
* HCWs with pulmonary or laryngeal TB pose a risk to patients and other
HCWs while they are infectious, and they should be excluded from the workplace
until they are noninfectious. The same work restrictions apply to all HCWs
regardless of their immune status.
* Before the HCW who has TB can return to the work-place, the health-care
facility should have documentation from the HCW's health-care provider
that the HCW is receiving adequate therapy, the cough has resolved, and
the HCW has had three consecutive negative sputum smears collected on different
days. After work duties are resumed and while the HCW remains on anti-TB
therapy, facility staff should receive periodic documentation from the
HCW's health-care provider that the HCW is being maintained on effective
drug therapy for the recommended time period and that the sputum AFB smears
continue to be negative.
* HCWs with active laryngeal or pulmonary TB who discontinue treatment
before they are cured should be evaluated promptly for infectiousness.
If the evaluation determines that they are still infectious, they should
be excluded from the workplace until treatment has been resumed, an adequate
response to therapy has been documented, and three more consecutive sputum
AFB smears collected on different days have been negative.
* HCWs who have TB at sites other than the lung or larynx usually do
not need to be excluded from the workplace if a diagnosis of concurrent
pulmonary TB has been ruled out.
2) Latent TB infection
* HCWs receiving preventive treatment for latent TB infection should
not be restricted from their usual work activities.
* HCWs with latent TB infection who cannot take or who do not accept
or complete a full course of preventive therapy should not be excluded
from the work-place. These HCWs should be counseled about the risk for
developing active TB and instructed regularly to seek prompt evaluation
if signs or symptoms develop that could be caused by TB.
K. Problem Evaluation
Epidemiologic investigations may be indicated for several situations.
These include, but are not limited to, a) the occurrence of PPD test conversions
or active TB in HCWs; b) the occurrence of possible person-to-person transmission
of M. tuberculosis; and c) situations in which patients or HCWs with active
TB are not promptly identified and isolated, thus exposing other persons
in the facility to M. tuberculosis. The general objectives of the epidemiologic
investigations in these situations are as follows:
1) to determine the likelihood that transmission of and infection with
M. tuberculosis has occurred in the facility;
2) to determine the extent to which M. tuberculosis has been transmitted;
3) to identify those persons who have been exposed and infected, enabling
them to receive appropriate clinical management;
4) to identify factors that could have contributed to transmission and
infection and to implement appropriate interventions; and
5) to evaluate the effectiveness of any interventions that are implemented
and to ensure that exposure to and transmission of M. tuberculosis have
been terminated.
The exact circumstances of these situations are likely to vary considerably,
and the associated epidemiologic investigations should be tailored to the
individual circumstances. The following sections provide general guidance
for conducting these investigations.
1. Investigating PPD test conversions and active TB in HCWs
a. Investigating PPD test conversions in HCWs
PPD test conversions may be detected in HCWs as a result of a contact
investigation, in which case the probable source of exposure and transmission
is already known (Section II.K.3.), or as a result of routine screening,
in which case the probable source of exposure and infection is not already
known and may not be immediately apparent.
If a skin-test conversion in an HCW is identified as part of routine
screening, the following steps should be considered (Figure 2):
* The HCW should be evaluated promptly for active TB. The initial evaluation
should include a thorough history, physical examination, and chest radiograph.
On the basis of the initial evaluation, other diagnostic procedures (e.g.,
sputum examination) may be indicated.
* If appropriate, the HCW should be placed on preventive or curative
therapy in accordance with current guidelines (Suppl. 2) (5).
* A history of possible exposure to M. tuberculosis should be obtained
from the HCW to determine the most likely source of infection. When the
source of infection is known, the drug-susceptibility pattern of the M.
tuberculosis isolate from the source patient should be identified to determine
appropriate preventive or curative therapy regimens.
* If the history suggests that the HCW was exposed to and infected with
M. tuberculosis outside the facility, no further epidemiologic investigation
to identify a source in the facility is necessary.
* If the history does not suggest that the HCW was exposed and infected
outside the facility but does identify a probable source of exposure in
the facility, contacts of the suspected source patient should be identified
and evaluated. Possible reasons for the exposure and transmission should
be evaluated (Table 4), interventions should be implemented to correct
these causes, and PPD testing of PPD-negative HCWs should be performed
immediately and repeated after 3 months.
If no additional PPD test conversions are detected on follow-up testing,
the investigation can be terminated.
If additional PPD test conversions are detected on follow-up testing,
the possible reasons for exposure and transmission should be reassessed,
the appropriateness of and degree of adherence to the interventions implemented
should be evaluated, and PPD testing of PPD-negative HCWs should be repeated
after another 3 months.
If no additional PPD test conversions are detected on the second round
of follow-up testing, the investigation can be terminated. However, if
additional PPD conversions are detected on the second round of follow-up
testing, a high-risk protocol should be implemented in the affected area
or occupational group, and the public health department or other persons
with expertise in TB infection control should be consulted.
* If the history does not suggest that the HCW was exposed to and infected
with M. tuberculosis outside the facility and does not identify a probable
source of exposure in the facility, further investigation to identify the
probable source patient in the facility is warranted.
The interval during which the HCW could have been infected should be
estimated. Generally, this would be the interval from 10 weeks before the
most recent negative PPD test through 2 weeks before the first positive
PPD test (i.e., the conversion).
Laboratory and infection-control records should be reviewed to identify
all patients or HCWs who have suspected or confirmed infectious TB and
who could have transmitted M. tuberculosis to the HCW.
If this process does identify a likely source patient, contacts of the
suspected source patient should be identified and evaluated, and possible
reasons for the exposure and transmission should be evaluated (Table 4).
Interventions should be implemented to correct these causes, and PPD testing
of PPD-negative HCWs should be repeated after 3 months. However, if this
process does not identify a probable source case, PPD screening results
of other HCWs in the same area or occupational group should be reviewed
for additional evidence of M. tuberculosis transmission. If sufficient
additional PPD screening results are not available, appropriate personnel
should consider conducting additional PPD screening of other HCWs in the
same area or occupational group.
(For Figure 2, see printed copy)
(For Table 4, see printed copy)
If this review and/or screening does not identify additional PPD conversions,
nosocomial transmission is less likely, and the contact investigation can
probably be terminated. Whether the HCW's PPD test conversion resulted
from occupational exposure and infection is uncertain; however, the absence
of other data implicating nosocomial transmission suggests that the conversion
could have resulted from a) unrecognized exposure to M. tuberculosis outside
the facility; b) cross-reactivity with another antigen (e.g., nontuberculous
mycobacteria); c) errors in applying, reading, or interpreting the test;
d) false positivity caused by the normal variability of the test; or e)
false positivity caused by a defective PPD preparation.
If this review and/or screening does identify additional PPD test conversions,
nosocomial transmission is more likely. In this situation, the patient
identification (i.e., triage) process, TB infection-control policies and
practices, and engineering controls should be evaluated to identify problems
that could have led to exposure and transmission (Table 4).
If no such problems are identified, a high-risk protocol should be implemented
in the affected area or occupational group, and the public health department
or other persons with expertise in TB infection control should be consulted.
If such problems are identified, appropriate interventions should be
implemented to correct the problem(s), and PPD skin testing of PPD-negative
HCWs should be repeated after 3 months.
If no additional PPD conversions are detected on follow-up testing,
the investigation can be terminated.
If additional PPD conversions are detected on follow-up testing, the
possible reasons for exposure and transmission should be reassessed, the
appropriateness of and adherence to the interventions implemented should
be evaluated, and PPD skin testing of PPD-negative HCWs should be repeated
after another 3 months.
If no additional PPD test conversions are detected on this second round
of follow-up testing, the investigation can be terminated. However, if
additional PPD test conversions are detected on the second round of follow-up
testing, a high-risk protocol should be implemented in the affected area
or occupational group, and the public health department or other persons
with expertise in TB infection control should be consulted.
b. Investigating cases of active TB in HCWs
If an HCW develops active TB, the following steps should be taken:
* The case should be evaluated epidemiologically, in a manner similar
to PPD test conversions in HCWs, to determine the likelihood that it resulted
from occupational transmission and to identify possible causes and implement
appropriate interventions if the evaluation suggests such transmission.
* Contacts of the HCW (e.g., other HCWs, patients, visitors, and others
who have had intense exposure to the HCW) should be identified and evaluated
for TB infection and disease (Section II.K.3; Suppl. 2). The public health
department should be notified immediately for consultation and to allow
for investigation of community contacts who were not exposed in the health-care
facility.
* The public health department should notify facilities when HCWs with
TB are reported by physicians so that an investigation of contacts can
be conducted in the facility. The information provided by the health department
to facilities should be in accordance with state or local laws to protect
the confidentiality of the HCW.
2. Investigating possible patient-to-patient transmission of M.
tuberculosis
Surveillance of active TB cases in patients should be conducted. If
this surveillance suggests the possibility of patient-to-patient transmission
of M. tuberculosis (e.g., a high proportion of TB patients had prior admissions
during the year preceding onset of their TB, the number of patients with
drug-resistant TB increased suddenly, or isolates obtained from multiple
patients had identical and characteristic drug-susceptibility or DNA fingerprint
patterns), the following steps should be taken:
* Review the HCW PPD test results and patient surveillance data for
the suspected areas to detect additional patients or HCWs with PPD test
conversions or active disease.
* Look for possible exposures that patients with newly diagnosed TB
could have had to other TB patients during previous admissions. For example,
were the patients admitted to the same room or area, or did they receive
the same procedure or go to the same treatment area on the same day?
If the evaluation thus far suggests transmission has occurred, the following
steps should be taken:
* Evaluate possible causes of the transmission (e.g., problem with patient
detection, institutional barriers to implementing appropriate isolation
practices, or inadequate engineering controls) (Table 4).
* Ascertain whether other patients or HCWs could have been exposed;
if so, evaluate these persons for TB infection and disease (Section II.K.3;
Suppl. 2).
* Notify the public health department so they can begin a community
contact investigation if necessary.
3. Investigating contacts of patients and HCWs who have infectious
TB
If a patient who has active TB is examined in a health-care facility
and the illness is not diagnosed correctly, resulting in failure to apply
appropriate precautions, or if an HCW develops active TB and exposes other
persons in the facility, the following steps should be taken when the illness
is later diagnosed correctly:
* To identify other patients and HCWs who were exposed to the source
patient before isolation procedures were begun, interview the source patient
and all applicable personnel and review that patient's medical record.
Determine the areas of the facility in which the source patient was hospitalized,
visited, or worked before being placed in isolation (e.g., outpatient clinics,
hospital rooms, treatment rooms, radiology and procedure areas, and patient
lounges) and the HCWs who may have been exposed during that time (e.g.,
persons providing direct care, therapists, clerks, transportation personnel,
housekeepers, and social workers).
* The contact investigation should first determine if M. tuberculosis
transmission has occurred from the source patient to those persons with
whom the source patient had the most intense contact.
* Administer PPD tests to the most intensely exposed HCWs and patients
as soon as possible after the exposure has occurred. If transmission did
occur to the most intensely exposed persons, then those persons with whom
the patient had less contact should be evaluated. If the initial PPD test
result is negative, a second test should be administered 12 weeks after
the exposure was terminated.
* Those persons who were exposed to M. tuberculosis and who have either
a PPD test conversion or symptoms suggestive of TB should receive prompt
clinical evaluation and, if indicated, chest radiographs and bacteriologic
studies should be performed (Suppl. 2). Those persons who have evidence
of newly acquired infection or active disease should be evaluated for preventive
or curative therapy (Suppl. 2). Persons who have previously had positive
PPD test results and who have been exposed to an infectious TB patient
do not require a repeat PPD test or a chest radiograph unless they have
symptoms suggestive of TB.
* In addition to PPD testing those HCWs and patients who have been exposed
to M. tuberculosis because a patient was not isolated promptly or an HCW
with active TB was not identified promptly, the investigation should determine
why the diagnosis of TB was delayed. If the correct diagnosis was made
but the patient was not isolated promptly, the reasons for the delay need
to be defined so that corrective actions can be taken.
L. Coordination with the Public Health Department
* As soon as a patient or HCW is known or suspected to have active TB,
the patient or HCW should be reported to the public health department so
that appropriate follow-up can be arranged and a community contact investigation
can be performed. The health department should be notified well before
patient discharge to facilitate follow-up and continuation of therapy.
A discharge plan coordinated with the patient or HCW, the health department,
and the inpatient facility should be implemented.
* The public health department should protect the confidentiality of
the patient or HCW in accordance with state and local laws.
* Health-care facilities and health departments should coordinate their
efforts to perform appropriate contact investigations on patients and HCWs
who have active TB.
* In accordance with state and local laws and regulations, results of
all AFB-positive sputum smears, cultures positive for M. tuberculosis,
and drug-susceptibility results on M. tuberculosis isolates should be reported
to the public health department as soon as these results are available.
* The public health department may be able to assist facilities with
planning and implementing various aspects of a TB infection-control program
(e.g., surveillance, screening activities, and outbreak investigations).
In addition, the state health department may be able to provide names of
experts to assist with the engineering aspects of TB infection control.
M. Additional Considerations for Selected Areas in Health-Care
Facilities and Other Health-Care Settings
This section contains additional information for selected areas in health-care
facilities and for other health-care settings.
1. Selected areas in health-care facilities
a. Operating rooms
* Elective operative procedures on patients who have TB should be delayed
until the patient is no longer infectious.
* If operative procedures must be performed, they should be done, if
possible, in operating rooms that have anterooms. For operating rooms without
anterooms, the doors to the operating room should be closed, and traffic
into and out of the room should be minimal to reduce the frequency of opening
and closing the door. Attempts should be made to perform the procedure
at a time when other patients are not present in the operative suite and
when a minimum number of personnel are present (e.g., at the end of day).
* Placing a bacterial filter on the patient endotracheal tube (or at
the expiratory side of the breathing circuit of a ventilator or anesthesia
machine if these are used) when operating on a patient who has confirmed
or suspected TB may help reduce the risk for contaminating anesthesia equipment
or discharging tubercle bacilli into the ambient air.
* During postoperative recovery, the patient should be monitored and
should be placed in a private room that meets recommended standards for
ventilating TB isolation rooms.
* When operative procedures (or other procedures requiring a sterile
field) are performed on patients who may have infectious TB, respiratory
protection worn by the HCW must protect the field from the respiratory
secretions of the HCW and protect the HCW from the infectious droplet nuclei
generated by the patient. Valved or positive-pressure respirators do not
protect the sterile field; therefore, a respirator that does not have a
valve and that meets the criteria in Section II.G should be used.
b. Autopsy rooms
* Because infectious aerosols are likely to be present in autopsy rooms,
such areas should be at negative pressure with respect to adjacent areas
(Suppl. 3), and the room air should be exhausted directly to the outside
of the building. ASHRAE recommends that autopsy rooms have ventilation
that provides an airflow of 12 ACH (47), although the effectiveness of
this ventilation level in reducing the risk for M. tuberculosis transmission
has not been evaluated. Where possible, this level should be increased
by means of ventilation system design or by auxiliary methods (e.g., recirculation
of air within the room through HEPA filters) (Suppl. 3).
* Respiratory protection should be worn by personnel while performing
autopsies on deceased persons who may have had TB at the time of death
(Section II.G; Suppl. 4).
* Recirculation of HEPA-filtered air within the room or UVGI may be
used as a supplement to the recommended ventilation (Suppl. 3).
c. Laboratories
* Laboratories in which specimens for mycobacteriologic studies (e.g.,
AFB smears and cultures) are processed should be designed to conform with
criteria specified by CDC and the National Institutes of Health (59).
2. Other health-care settings
TB precautions may be appropriate in a number of other types of health-care
settings. The specific precautions that are applied will vary depending
on the setting. At a minimum, a risk assessment should be performed yearly
for these settings; a written TB infection-control plan should be developed,
evaluated, and revised on a regular basis; protocols should be in place
for identifying and managing patients who may have active TB; HCWs should
receive appropriate training, education, and screening; protocols for problem
evaluation should be in place; and coordination with the public health
department should be arranged when necessary. Other recommendations specific
to certain of these settings follow.
a. Emergency medical services
* When EMS personnel or others must transport patients who have confirmed
or suspected active TB, a surgical mask should be placed, if possible,
over the patient's mouth and nose. Because administrative and engineering
controls during emergency transport situations cannot be ensured, EMS personnel
should wear respiratory protection when transporting such patients. If
feasible, the windows of the vehicle should be kept open. The heating and
air-conditioning system should be set on a nonrecirculating cycle.
* EMS personnel should be included in a comprehensive PPD screening
program and should receive a baseline PPD test and follow-up testing as
indicated by the risk assessment. They should also be included in the follow-up
of contacts of a patient with infectious TB.*
__________ * The Ryan White Comprehensive AIDS Resource Emergency Act
of 1990, P.L. 101-381, mandates notification of EMS personnel after they
have been exposed to infectious pulmonary TB (42 U.S.C. 300ff-82.54 Fed.
Reg. 13417 [March 21, 1994]).
b. Hospices
* Hospice patients who have confirmed or suspected TB should be managed
in the manner described in this document for management of TB patients
in hospitals. General-use and specialized areas (e.g., treatment or TB
isolation rooms) should be ventilated in the same manner as described for
similar hospital areas.
c. Long-term care facilities
* Recommendations published previously for preventing and controlling
TB in long-term care facilities should be followed (60).
* Long-term care facilities should also follow the recommendations outlined
in this document.
d. Correctional facilities
* Recommendations published previously for preventing and controlling
TB in correctional facilities should be followed (61).
* Prison medical facilities should also follow the recommendations outlined
in this document.
e. Dental settings
In general, the symptoms for which patients seek treatment in a dental-care
setting are not likely to be caused by infectious TB. Unless a patient
requiring dental care coincidentally has TB, it is unlikely that infectious
TB will be encountered in the dental setting. Furthermore, generation of
droplet nuclei containing M. tuberculosis during dental procedures has
not been demonstrated (62). Therefore, the risk for transmission of M.
tuberculosis in most dental settings is probably quite low. Nevertheless,
during dental procedures, patients and dental workers share the same air
for varying periods of time. Coughing may be stimulated occasionally by
oral manipulations, although no specific dental procedures have been classified
as "cough-inducing." In some instances, the population served by a dental-care
facility, or the HCWs in the facility, may be at relatively high risk for
TB. Because the potential exists for transmission of M. tuberculosis in
dental settings, the following recommendations should be followed:
* A risk assessment (Section II.B) should be done periodically, and
TB infection-control policies for each dental setting should be based on
the risk assessment. The policies should include provisions for detection
and referral of patients who may have undiagnosed active TB; management
of patients with active TB, relative to provision of urgent dental care;
and employer-sponsored HCW education, counseling, and screening.
* While taking patients' initial medical histories and at periodic updates,
dental HCWs should routinely ask all patients whether they have a history
of TB disease and symptoms suggestive of TB.
* Patients with a medical history or symptoms suggestive of undiagnosed
active TB should be referred promptly for medical evaluation of possible
infectiousness. Such patients should not remain in the dental-care facility
any longer than required to arrange a referral. While in the dental-care
facility, they should wear surgical masks and should be instructed to cover
their mouths and noses when coughing or sneezing.
* Elective dental treatment should be deferred until a physician confirms
that the patient does not have infectious TB. If the patient is diagnosed
as having active TB, elective dental treatment should be deferred until
the patient is no longer infectious.
* If urgent dental care must be provided for a patient who has, or is
strongly suspected of having, infectious TB, such care should be provided
in facilities that can provide TB isolation (Sections II.E and G). Dental
HCWs should use respiratory protection while performing procedures on such
patients.
* Any dental HCW who has a persistent cough (i.e., a cough lasting greater
than or equal to 3 weeks), especially in the presence of other signs or
symptoms compatible with active TB (e.g., weight loss, night sweats, bloody
sputum, anorexia, and fever), should be evaluated promptly for TB. The
HCW should not return to the work-place until a diagnosis of TB has been
excluded or until the HCW is on therapy and a determination has been made
that the HCW is noninfectious.
* In dental-care facilities that provide care to populations at high
risk for active TB, it may be appropriate to use engineering controls similar
to those used in general-use areas (e.g., waiting rooms) of medical facilities
that have a similar risk profile.
f. Home-health-care settings
* HCWs who provide medical services in the homes of patients who have
suspected or confirmed infectious TB should instruct such patients to cover
their mouths and noses with a tissue when coughing or sneezing. Until such
patients are no longer infectious, HCWs should wear respiratory protection
when entering these patients' homes (Suppl. 4).
* Precautions in the home may be discontinued when the patient is no
longer infectious (Suppl. 1).
* HCWs who provide health-care services in their patients' homes can
assist in preventing transmission of M. tuberculosis by educating their
patients regarding the importance of taking medications as prescribed and
by administering DOT.
* Cough-inducing procedures performed on patients who have infectious
TB should not be done in the patients' homes unless absolutely necessary.
When medically necessary cough-inducing procedures (e.g., AFB sputum collection
for evaluation of therapy) must be performed on patients who may have infectious
TB, the procedures should be performed in a health-care facility in a room
or booth that has the recommended ventilation for such procedures. If these
procedures must be performed in a patient's home, they should be performed
in a well-ventilated area away from other household members. If feasible,
the HCW should consider opening a window to improve ventilation or collecting
the specimen while outside the dwelling. The HCW collecting these specimens
should wear respiratory protection during the procedure (Section II.G).
* HCWs who provide medical services in their patients' homes should
be included in comprehensive employer-sponsored TB training, education,
counseling, and screening programs. These programs should include provisions
for identifying HCWs who have active TB, baseline PPD skin testing, and
follow-up PPD testing at intervals appropriate to the degree of risk.
* Patients who are at risk for developing active TB and the HCWs who
provide medical services in the homes of such patients should be reminded
periodically of the importance of having pulmonary symptoms evaluated promptly
to permit early detection of and treatment for TB.
g. Medical offices
In general, the symptoms of active TB are symptoms for which patients
are likely to seek treatment in a medical office. Furthermore, the populations
served by some medical offices, or the HCWs in the office, may be at relatively
high risk for TB. Thus, it is likely that infectious TB will be encountered
in a medical office. Because of the potential for M. tuberculosis transmission,
the following recommendations should be observed:
* A risk assessment should be conducted periodically, and TB infection-control
policies based on results of the risk assessment should be developed for
the medical office. The policies should include provisions for identifying
and managing patients who may have undiagnosed active TB; managing patients
who have active TB; and educating, training, counseling, and screening
HCWs.
* While taking patients' initial medical histories and at periodic updates,
HCWs who work in medical offices should routinely ask all patients whether
they have a history of TB disease or have had symptoms suggestive of TB.
* Patients with a medical history and symptoms suggestive of active
TB should receive an appropriate diagnostic evaluation for TB and be evaluated
promptly for possible infectiousness. Ideally, this evaluation should be
done in a facility that has TB isolation capability. At a minimum, the
patient should be provided with and asked to wear a surgical mask, instructed
to cover the mouth and nose with a tissue when coughing or sneezing, and
separated as much as possible from other patients.
* Medical offices that provide evaluation or treatment services for
TB patients should follow the recommendations for managing patients in
ambulatory-care settings (Section II.D).
* If cough-inducing procedures are to be administered in a medical office
to patients who may have active TB, appropriate precautions should be followed
(Section II.H).
* Any HCW who has a persistent cough (i.e., a cough lasting greater
than or equal to 3 weeks), especially in the presence of other signs or
symptoms compatible with active TB (e.g., weight loss, night sweats, bloody
sputum, anorexia, or fever) should be evaluated promptly for TB. HCWs with
such signs or symptoms should not return to the workplace until a diagnosis
of TB has been excluded or until they are on therapy and a determination
has been made that they are noninfectious.
* HCWs who work in medical offices in which there is a likelihood of
exposure to patients who have infectious TB should be included in employer-sponsored
education, training, counseling, and PPD testing programs appropriate to
the level of risk in the office.
* In medical offices that provide care to populations at relatively
high risk for active TB, use of engineering controls as described in this
document for general-use areas (e.g., waiting rooms) may be appropriate
(Section II.F; Suppl. 3).
Supplement 1: Determining the Infectiousness of a TB Patient
The infectiousness of patients with TB correlates with the number of
organisms expelled into the air, which, in turn, correlates with the following
factors: a) disease in the lungs, airways, or larynx; b) presence of cough
or other forceful expiratory measures; c) presence of acid-fast bacilli
(AFB) in the sputum; d) failure of the patient to cover the mouth and nose
when coughing; e) presence of cavitation on chest radiograph; f) inappropriate
or short duration of chemotherapy; and g) administration of procedures
that can induce coughing or cause aerosolization of M. tuberculosis (e.g.,
sputum induction).
The most infectious persons are most likely those who have not been
treated for TB and who have either a) pulmonary or laryngeal TB and a cough
or are undergoing cough-inducing procedures, b) a positive AFB sputum smear,
or c) cavitation on chest radiograph. Persons with extrapulmonary TB usually
are not infectious unless they have a) concomitant pulmonary disease; b)
nonpulmonary disease located in the respiratory tract or oral cavity; or
c) extrapulmonary disease that includes an open abscess or lesion in which
the concentration of organisms is high, especially if drainage from the
abscess or lesion is extensive (20,22). Coinfection with HIV does not appear
to affect the infectiousness of TB patients (63-65).
In general, children who have TB may be less likely than adults to be
infectious; however, transmission from children can occur. Therefore, children
with TB should be evaluated for infectiousness using the same parameters
as for adults (i.e., pulmonary or laryngeal TB, presence of cough or cough-inducing
procedures, positive sputum AFB smear, cavitation on chest radiograph,
and adequacy and duration of therapy). Pediatric patients who may be infectious
include those who a) are not on therapy, b) have just been started on therapy,
or c) are on inadequate therapy, and who a) have laryngeal or extensive
pulmonary involvement, b) have pronounced cough or are undergoing cough-inducing
procedures, c) have positive sputum AFB smears, or d) have cavitary TB.
Children who have typical primary tuberculous lesions and do not have any
of the indicators of infectiousness listed previously usually do not need
to be placed in isolation. Because the source case for pediatric TB patients
often occurs in a member of the infected child's family (45), parents and
other visitors of all pediatric TB patients should be evaluated for TB
as soon as possible.
Infection is most likely to result from exposure to persons who have
unsuspected pulmonary TB and are not receiving anti-TB therapy or from
persons who have diagnosed TB and are not receiving adequate therapy. Administration
of effective anti-TB therapy has been associated with decreased infectiousness
among persons who have active TB (66). Effective therapy reduces coughing,
the amount of sputum produced, and the number of organisms in the sputum.
However, the period of time a patient must take effective therapy before
becoming noninfectious varies between patients (67). For example, some
TB patients are never infectious, whereas those with unrecognized or inadequately
treated drug-resistant TB may remain infectious for weeks or months (24).
Thus, decisions about infectiousness should be made on an individual basis.
In general, patients who have suspected or confirmed active TB should
be considered infectious if they a) are coughing, b) are undergoing cough-inducing
procedures, or c) have positive AFB sputum smears, and if they a) are not
on chemotherapy, b) have just started chemotherapy, or c) have a poor clinical
or bacteriologic response to chemotherapy. A patient who has drug-susceptible
TB and who is on adequate chemotherapy and has had a significant clinical
and bacteriologic response to therapy (i.e., reduction in cough, resolution
of fever, and progressively decreasing quantity of bacilli on smear) is
probably no longer infectious. However, because drug-susceptibility results
are not usually known when the decision to discontinue isolation is made,
all TB patients should remain in isolation while hospitalized until they
have had three consecutive negative sputum smears collected on different
days and they demonstrate clinical improvement.
Supplement 2: Diagnosis and Treatment of Latent TB Infection and
Active TB
I. Diagnostic Procedures for TB Infection and Disease
A diagnosis of TB may be considered for any patient who has a persistent
cough (i.e., a cough lasting greater than or equal to 3 weeks) or other
signs or symptoms compatible with TB (e.g., bloody sputum, night sweats,
weight loss, anorexia, or fever). However, the index of suspicion for TB
will vary in different geographic areas and will depend on the prevalence
of TB and other characteristics of the population served by the facility.
The index of suspicion for TB should be very high in areas or among groups
of patients in which the prevalence of TB is high (Section I.B). Persons
for whom a diagnosis of TB is being considered should receive appropriate
diagnostic tests, which may include PPD skin testing, chest radiography,
and bacteriologic studies (e.g., sputum microscopy and culture).
A. PPD Skin Testing and Anergy Testing
1. Application and reading of PPD skin tests
The PPD skin test is the only method available for demonstrating infection
with M. tuberculosis. Although currently available PPD tests are less than
100% sensitive and specific for detection of infection with M. tuberculosis,
no better diagnostic methods have yet been devised. Interpretation of PPD
test results requires knowledge of the antigen used, the immunologic basis
for the reaction to this antigen, the technique used to administer and
read the test, and the results of epidemiologic and clinical experience
with the test (2,5,6). The PPD test, like all medical tests, is subject
to variability, but many of the variations in administering and reading
PPD tests can be avoided by proper training and careful attention to details.
The intracutaneous (Mantoux) administration of a measured amount of
PPD-tuberculin is currently the preferred method for doing the test. One-tenth
milliliter of PPD (5 TU) is injected just beneath the surface of the skin
on either the volar or dorsal surface of the forearm. A discrete, pale
elevation of the skin (i.e., a wheal) that is 6-10 mm in diameter should
be produced.
PPD test results should be read by designated, trained personnel between
48 and 72 hours after injection. Patient or HCW self-reading of PPD test
results should not be accepted (68). The result of the test is based on
the presence or absence of an induration at the injection site. Redness
or erythema should not be measured. The transverse diameter of induration
should be recorded in millimeters.
2. Interpretation of PPD skin tests
a. General
The interpretation of a PPD reaction should be influenced by the purpose
for which the test was given (e.g., epidemiologic versus diagnostic purposes),
by the prevalence of TB infection in the population being tested, and by
the consequences of false classification. Errors in classification can
be minimized by establishing an appropriate definition of a positive reaction
(Table S2-1").
The positive-predictive value of PPD tests (i.e, the probability that
a person with a positive PPD test is actually infected with M. tuberculosis)
is dependent on the prevalence of TB infection in the population being
tested and the specificity of the test (69,70). In populations with a low
prevalence of TB infection, the probability that a positive PPD test represents
true infection with M. tuberculosis is very low if the cut-point is set
too low (i.e., the test is not adequately specific). In populations with
a high prevalence of TB infection, the probability that a positive PPD
test using the same cut-point represents true infection with M. tuberculosis
is much higher. To ensure that few persons infected with tubercle bacilli
will be misclassified as having negative reactions and few persons not
infected with tubercle bacilli will be misclassified as having positive
reactions, different cut-points are used to separate positive reactions
from negative reactions for different populations, depending on the risk
for TB infection in that population.
A lower cut-point (i.e., 5 mm) is used for persons in the highest risk
groups, which include HIV-infected persons, recent close contacts of persons
with TB (e.g., in the household or in an unprotected occupational exposure
similar in intensity and duration to household contact), and persons who
have abnormal chest radiographs with fibrotic changes consistent with inactive
TB. A higher cut-point (i.e., 10 mm) is used for persons who are not in
the highest risk group but who have other risk factors (e.g., injecting-drug
users known to be HIV seronegative; persons with certain medical conditions
that increase the risk for progression from latent TB infection to active
TB [Table S2-1]); medically under-served, low-income populations; persons
born in foreign countries that have a high prevalence of TB; and residents
of correctional institutions and nursing homes). An even higher cut-point
(i.e., 15 mm) is used for all other persons who have none of the above
risk factors.
Recent PPD converters are considered members of a high-risk group. A
greater than or equal to 10 mm increase in the size of the induration within
a 2-year period is classified as a conversion from a negative to a positive
test result for persons less than 35 years of age. An increase of induration
of greater than or equal to 15 mm within a 2-year period is classified
as a conversion for persons greater than or equal to 35 years of age (5).
b. HCWs
In general, HCWs should have their skin-test results interpreted according
to the recommendations in this supplement and in sections 1, 2, 3, and
5 of Table S2-1. However, the prevalence of TB in the facility should be
considered when choosing the appropriate cut-point for defining a positive
PPD reaction. In facilities where there is essentially no risk for exposure
to TB patients (i.e., minimal- or very low-risk facilities [Section II.B]),
an induration greater than or equal to 15 mm may be an appropriate cut-point
for HCWs who have no other risk factors. In other facilities where TB patients
receive care, the appropriate cut-point for HCWs who have no other risk
factors may be greater than or equal to 10 mm.
A recent PPD test conversion in an HCW should be defined generally as
an increase of greater than or equal to 10 mm in the size of induration
within a 2-year period. For HCWs in facilities where exposure to TB is
very unlikely (e.g., minimal-risk facilities), an increase of greater than
or equal to 15 mm within a 2-year period may be more appropriate for defining
a recent conversion because of the lower positive-predictive value of the
test in such groups.
3. Anergy testing
HIV-infected persons may have suppressed reactions to PPD skin tests
because of anergy, particularly if their CD4+ T-lymphocyte counts decline
(71). Persons with anergy will have a negative PPD test regardless of infection
with M. tuberculosis. HIV-infected testing (72). Two companion antigens
(e.g., Candida antigen and tetanus toxoid) should be administered in addition
to PPD. Persons with greater than or equal to 3 mm of induration to any
of the skin tests (including tuberculin) are considered not anergic. Reactions
of greater than or equal to 5 mm to PPD are considered to be evidence of
TB infection in HIV-infected persons regardless of the reactions to the
companion antigens. If there is no reaction (i.e., less than 3 mm induration)
to any of the antigens, the person being tested is considered anergic.
Determination of whether such persons are likely to be infected with M.
tuberculosis must be based on other epidemiologic factors (e.g., the proportion
of other persons with the same level of exposure who have positive PPD
test results and the intensity or duration of exposure to infectious TB
patients that the anergic person experienced).
4. Pregnancy and PPD skin testing
Although thousands (perhaps millions) of pregnant women have been PPD
skin tested since the test was devised, thus far no documented episodes
of fetal harm have resulted from use of the tuberculin test (73). Pregnancy
should not exclude a female HCW from being skin tested as part of a contact
investigation or as part of a regular skin-testing program.
TABLE S2-1. Summary of interpretation of purified protein derivation
(PPD-tubercilin skin-test results
-----------------------------------------------------------------------------
1. An induration of greater than or equals to 5 mm is classified as
positive in:
* persons who have human immunodeficiency virus (HIV) infection or risk
factors for HIV infection but unknown HIV status;
* persons who have had recent close contact* with persons who have active
tuberculosis (TB);
* Recent close contact inplies either househould or social contact or
unprotected occupational exposure similar in intensity and duration to
househould contact.
* persons who have fibrotic chest radiographs (consistent with healed
TB).
2. An induration of greater than or equals to 10 mm is classified as
positive in all persons who do not meet any of the criteria above but who
have other risk factors for TB, including:
High-risk groups--
* injection-drug users known to be HIV seronegative;
* persons who have other medical conditions that reportedly increase
the risk for progressing from latent TB infection to active TB (e.g., silicosis;
gastrectomy or jejuno-ioeal bypass; being greater than or equal to 10%
below ideal body weight; chronic renal failure with renal dialysis; diabetes
mellitus; high-dose corticosteroid or other immunosuppressive therapy;
some hematologic disorders, including malignancies such as leukemias and
lymphomas; and other malignancies);
* children less than or equal to 4 years of age.
High-prevalence groups--
* persons born in countries in Asia, Africa, the Caribbean, and Latin
America that have high prevalence of TB;
* persons from medically underserved, low-income populations;
* residents of long-term-care facilities (e.g., correctional institutions
and nursing homes);
* persons from high-risk populations in their communities, as determined
by local public health authorities.
3. An induration of greater than or equal to 15 mm is classified as
positive in persons who do not meet any of the above criteria.
4. Recent converters are defined on the basis of both size of induration
and age of the person being tested:
* Greater than or equal to 10 mm increase within a 2-year period is
classified as a recent conversion for persons less than or equal to 35
years of age;
* Greater than or equal to 15 mm increase within a 2-year period is
classified as a recent conversion for persons greater than or equal to
35 years of age.
5. PPD skin-test results in health-care workers (HCWs)
* In general, the recommendations in sections 1, 2, and 3 of this table
should be followed when interpreting skin-test results in HCWs.
* However, the prevalence of TB in the facility should be considered
when choosing the appropriate cut-point for defining a positive PPD reaction.
In facilities where there is essentially no risk for exposure to Mycobacterium
tuberculosis (i.e., minimal- or very low-risk facilities [Section II.B]),
an induration greater than or equal 15 mm may be a suitable cut-point for
HCWs who have no other risk factors. In facilities where TB patients receive
care, the cut-pint for HCWs with no other risk factors may be greater than
or equal 10 mm.
* A recent conversion in an HCW should be defined generally as a greater
than or equal to 10 mm increase in size of induration within a 2-year period.
For HCWs who work in facilities where exposure to TB is very unlikely (e.g.,
minimal-risk facilities), an increase of greater than or equal to 15 mm
within a 2-year period may be more appropriate for defining a recent conversion
because of the lower positive-predictive value of the test in such groups.
____________________________________________________________________________
5. BCG vaccination and PPD skin testing
BCG vaccination may produce a PPD reaction that cannot be distinguished
reliably from a reaction caused by infection with M. tuberculosis. For
a person who was vaccinated with BCG, the probability that a PPD test reaction
results from infection with M. tuberculosis increases a) as the size of
the reaction increases, b) when the person is a contact of a person with
TB, c) when the person's country of origin has a high prevalence of TB,
and d) as the length of time between vaccination and PPD testing increases.
For example, a PPD test reaction of greater than or equal to 10 mm probably
can be attributed to M. tuberculosis infection in an adult who was vaccinated
with BCG as a child and who is from a country with a high prevalence of
TB (74,75).
6. The booster phenomenon
The ability of persons who have TB infection to react to PPD may gradually
wane. For example, if tested with PPD, adults who were infected during
their childhood may have a negative reaction. However, the PPD could boost
the hypersensitivity, and the size of the reaction could be larger on a
subsequent test. This boosted reaction may be misinterpreted as a PPD test
conversion from a newly acquired infection. Misinterpretation of a boosted
reaction as a new infection could result in unnecessary investigations
of laboratory and patient records in an attempt to identify the source
case and in unnecessary prescription of preventive therapy for HCWs. Although
boosting can occur among persons in any age group, the likelihood of the
reaction increases with the age of the person being tested (6,76).
When PPD testing of adults is to be repeated periodically (as in HCW
skin-testing programs), two-step testing can be used to reduce the likelihood
that a boosted reaction is misinterpreted as a new infection. Two-step
testing should be performed on all newly employed HCWs who have an initial
negative PPD test result at the time of employment and have not had a documented
negative PPD test result during the 12 months preceding the initial test.
A second test should be performed 1-3 weeks after the first test. If the
second test result is positive, this is most likely a boosted reaction,
and the HCW should be classified as previously infected. If the second
test result remains negative, the HCW is classified as uninfected, and
a positive reaction to a subsequent test is likely to represent a new infection
with M. tuberculosis.
B. Chest Radiography
Patients who have positive skin-test results or symptoms suggestive
of TB should be evaluated with a chest radiograph regardless of PPD test
results. Radiographic abnormalities that strongly suggest active TB include
upper-lobe infiltration, particularly if cavitation is seen (77), and patchy
or nodular infiltrates in the apical or subapical posterior upper lobes
or the superior segment of the lower lobe. If abnormalities are noted,
or if the patient has symptoms suggestive of extrapulmonary TB, additional
diagnostic tests should be conducted.
The radiographic presentation of pulmonary TB in HIV-infected patients
may be unusual (78). Typical apical cavitary disease is less common among
such patients. They may have infiltrates in any lung zone, a finding that
is often associated with mediastinal and/or hilar adenopathy, or they may
have a normal chest radiograph, although this latter finding occurs rarely.
C. Bacteriology
Smear and culture examination of at least three sputum specimens collected
on different days is the main diagnostic procedure for pulmonary TB (6).
Sputum smears that fail to demonstrate AFB do not exclude the diagnosis
of TB. In the United States, approximately 60% of patients with positive
sputum cultures have positive AFB sputum smears. HIV-infected patients
who have pulmonary TB may be less likely than immunocompetent patients
to have AFB present on sputum smears, which is consistent with the lower
frequency of cavitary pulmonary disease observed among HIV-infected persons
(39,41).
Specimens for smear and culture should contain an adequate amount of
expectorated sputum but not much saliva. If a diagnosis of TB cannot be
established from sputum, a bronchoscopy may be necessary (36,37). In young
children who cannot produce an adequate amount of sputum, gastric aspirates
may provide an adequate specimen for diagnosis.
A culture of sputum or other clinical specimen that contains M. tuberculosis
provides a definitive diagnosis of TB. Conventional laboratory methods
may require 4-8 weeks for species identification; however, the use of radiometric
culture techniques and nucleic acid probes facilitates more rapid detection
and identification of mycobacteria (79,80). Mixed mycobacterial infection,
either simultaneous or sequential, can obscure the identification of M.
tuberculosis during the clinical evaluation and the laboratory analysis
(42). The use of nucleic acid probes for both M. avium complex and M. tuberculosis
may be useful for identifying mixed mycobacterial infections in clinical
specimens.
II. Preventive Therapy for Latent TB Infection and Treatment of Active
TB
A. Preventive Therapy for Latent TB Infection
Determining whether a person with a positive PPD test reaction or conversion
is a candidate for preventive therapy must be based on a) the likelihood
that the reaction represents true infection with M. tuberculosis (as determined
by the cut-points), b) the estimated risk for progression from latent infection
to active TB, and c) the risk for hepatitis associated with taking isoniazid
(INH) preventive therapy (as determined by age and other factors).
HCWs with positive PPD test results should be evaluated for preventive
therapy regardless of their ages if they a) are recent converters, b) are
close contacts of persons who have active TB, c) have a medical condition
that increases the risk for TB, d) have HIV infection, or e) use injecting
drugs (5). HCWs with positive PPD test results who do not have these risk
factors should be evaluated for preventive therapy if they are less than
35 years of age.
Preventive therapy should be considered for anergic persons who are
known contacts of infectious TB patients and for persons from populations
in which the prevalence of TB infection is very high (e.g., a prevalence
of greater than 10%).
Because the risk for INH-associated hepatitis may be increased during
the peripartum period, the decision to use preventive therapy during pregnancy
should be made on an individual basis and should depend on the patient's
estimated risk for progression to active disease. In general, preventive
therapy can be delayed until after delivery. However, for pregnant women
who were probably infected recently or who have high-risk medical conditions,
especially HIV infection, INH preventive therapy should begin when the
infection is documented (81-84). No evidence suggests that INH poses a
carcinogenic risk to humans (85-87).
The usual preventive therapy regimen is oral INH 300 mg daily for adults
and 10 mg/kg/day for children (88). The recommended duration of therapy
is 12 months for persons with HIV infection and 9 months for children.
Other persons should receive INH therapy for 6-12 months. For persons who
have silicosis or a chest radiograph demonstrating inactive fibrotic lesions
and who have no evidence of active TB, acceptable regimens include a) 4
months of INH plus rifampin or b) 12 months of INH, providing that infection
with INH-resistant organisms is unlikely (33). For persons likely to be
infected with MDR-TB, alternative multidrug preventive therapy regimens
should be considered (89).
All persons placed on preventive therapy should be educated regarding
the possible adverse reactions associated with INH use, and they should
be questioned carefully at monthly intervals by qualified personnel for
signs or symptoms consistent with liver damage or other adverse effects
(81-84,88,90,91). Because INH-associated hepatitis occurs more frequently
among persons greater than 35 years of age, a transaminase measurement
should be obtained from persons in this age group before initiation of
INH therapy and then obtained monthly until treatment has been completed.
Other factors associated with an increased risk for hepatitis include daily
alcohol use, chronic liver disease, and injecting-drug use. In addition,
postpubertal black and Hispanic women may be at greater risk for hepatitis
or drug interactions (92). More careful clinical monitoring of persons
with these risk factors and possibly more frequent laboratory monitoring
should be considered. If any of these tests exceeds three to five times
the upper limit of normal, discontinuation of INH should be strongly considered.
Liver function tests are not a substitute for monthly clinical evaluations
or for the prompt assessment of signs or symptoms of adverse reactions
that could occur between the regularly scheduled evaluations (33).
Persons who have latent TB infection should be advised that they can
be reinfected with another strain of M. tuberculosis (93).
B. Treatment of Patients Who Have Active TB
Drug-susceptibility testing should be performed on all initial isolates
from patients with TB. However, test results may not be available for several
weeks, making selection of an initial regimen difficult, especially in
areas where drug-resistant TB has been documented. Current recommendations
for therapy and dosage schedules for the treatment of drug-susceptible
TB should be followed (Table S2-2) (43). Streptomycin is contraindicated
in the treatment of pregnant women because of the risk for ototoxicity
to the fetus. In geographic areas or facilities in which drug-resistant
TB is highly prevalent, the initial treatment regimen used while results
of drug-susceptibility tests are pending may need to be expanded. This
decision should be based on analysis of surveillance data.
When results from drug-susceptibility tests become available, the regimen
should be adjusted appropriately (94-97). If drug resistance is present,
clinicians unfamiliar with the management of patients with drug-resistant
TB should seek expert consultation.
For any regimen to be effective, adherence to the regimen must be ensured.
The most effective method of ensuring adherence is the use of DOT after
the patient has been discharged from the hospital (43,91). This practice
should be coordinated with the public health department.
(For Table S2-2, see printed copy)
(For Table S2-3, see printed copy)
Supplement 3: Engineering Controls
I. Introduction
This supplement provides information regarding the use of ventilation
(Section II) and UVGI (Section III) for preventing the transmission of
M. tuberculosis in health-care facilities. The information provided is
primarily conceptual and is intended to educate staff in the health-care
facility concerning engineering controls and how these controls can be
used as part of the TB infection-control program. This supplement should
not be used in place of consultation with experts, who can assume responsibility
for advising on ventilation system design and selection, installation,
and maintenance of equipment.
The recommendations for engineering controls include a) local exhaust
ventilation (i.e., source control), b) general ventilation, and c) air
cleaning. General ventilation considerations include a) dilution and removal
of contaminants, b) airflow patterns within rooms, c) airflow direction
in facilities, d) negative pressure in rooms, and e) TB isolation rooms.
Air cleaning or disinfection can be accomplished by filtration of air (e.g.,
through HEPA filters) or by UVGI.
II. Ventilation
Ventilation systems for health-care facilities should be designed, and
modified when necessary, by ventilation engineers in collaboration with
infection-control and occupational health staff. Recommendations for designing
and operating ventilation systems have been published by ASHRAE (47), AIA
(48), and the American Conference of Governmental Industrial Hygienists,
Inc. (98).
As part of the TB infection-control plan, health-care facility personnel
should determine the number of TB isolation rooms, treatment rooms, and
local exhaust devices (i.e., for cough-inducing or aerosol-generating procedures)
that the facility needs. The locations of these rooms and devices will
depend on where in the facility the ventilation conditions recommended
in this document can be achieved. Grouping isolation rooms together in
one area of the facility may facilitate the care of TB patients and the
installation and maintenance of optimal engineering controls (particularly
ventilation).
Periodic evaluations of the ventilation system should review the number
of TB isolation rooms, treatment rooms, and local exhaust devices needed
and the regular maintenance and monitoring of the local and general exhaust
systems (including HEPA filtration systems if they are used).
The various types and conditions of ventilation systems in health-care
facilities and the individual needs of these facilities preclude the ability
to provide specific instructions regarding the implementation of these
recommendations. Engineering control methods must be tailored to each facility
on the basis of need and the feasibility of using the ventilation and air-cleaning
concepts discussed in this supplement.
A. Local Exhaust Ventilation
Purpose: To capture airborne contaminants at or near their source (i.e.,
the source control method) and remove these contaminants without exposing
persons in the area to infectious agents (98).
Source control techniques can prevent or reduce the spread of infectious
droplet nuclei into the general air circulation by entrapping infectious
droplet nuclei as they are being emitted by the patient (i.e., the source).
These techniques are especially important when performing procedures likely
to generate aerosols containing infectious particles and when infectious
TB patients are coughing or sneezing.
Local exhaust ventilation is a preferred source control technique, and
it is often the most efficient way to contain airborne such as leukemias
and lymphomas; and other source before they can disperse. Therefore, the
technique should be used, if feasible, wherever aerosol-generating procedures
are performed. Two basic types of local exhaust devices use hoods: a) the
enclosing type, in which the hood either partially or fully encloses the
infectious source; and b) the exterior type, in which the infectious source
is near but outside the hood. Fully enclosed hoods, booths, or tents are
always preferable to exterior types because of their superior ability to
prevent contaminants from escaping into the HCW's breathing zone. Descriptions
of both enclosing and exterior devices have been published previously (98).
1. Enclosing devices
The enclosing type of local exhaust ventilation device includes laboratory
hoods used for processing specimens that could contain viable infectious
organisms, booths used for sputum induction or administration of aerosolized
medications (e.g., aerosolized pentamidine) (Figure S3-1), and tents or
hoods made of vinyl or other materials used to enclose and isolate a patient.
These devices are available in various configurations. The most simple
of these latter devices is a tent that is placed over the patient; the
tent has an exhaust connection to the room discharge exhaust system. The
most complex device is an enclosure that has a sophisticated self-contained
airflow and recirculation system.
Both tents and booths should have sufficient airflow to remove at least
99% of airborne particles during the interval between the departure of
one patient and the arrival of the next (99). The time required for removing
a given percentage of airborne particles from an enclosed space depends
on several factors. These factors include the number of ACH, which is determined
by the number of cubic feet of air in the room or booth and the rate at
which air is entering the room or booth at the intake source; the location
of the ventilation inlet and outlet; and the physical configuration of
the room or booth (Table S3-1).
TABLE S3-1. Air changes per hour (ACH) and time in minutes required
for removal efficiencies of 90%, 99%, and 99.9% of airborne contaminants*
-----------------------------------------------------------------------------
Minutes required for a removal efficiency of: ---------------------------------------------
ACH 90% 99% 99.9% -----------------------------------------------------------------------------
1 138 276 414 2 69 138 207 3 46 92 138 4 35 69 104 5 28 55 83
6 23 46 69 7 20 39 59 8 17 35 52 9 15 31 46 10 14 28 41
11 13 25 38 12 12 23 35 13 11 21 32 14 10 20 30 15 9 18 28
16 9 17 26 17 8 16 24 18 8 15 23 19 7 15 22 20 7 14 21
25 6 11 17 30 5 9 14 35 4 8 12 40 3 7 10 45 3 6 9 50 3 6 8
-----------------------------------------------------------------------------
* This table has been adapted from the formula for the rate of purging
airborne contaminats (99). Values have been derived from the formula t(1)
= [In (C(2) divide C(1) + (Q divide V)] x 60, with T(1) = 0 and C(2) divide
C(1) - (removal efficiency divide 100), and where:
t(1) = initial timepoint C(1) = initial concentration of contaminant
C(2) = final concentration of contaminants Q = air flow rate (cubic feet
per hour) V = room volume (cubic feet) Q divide V = ACH
The times given assume perfect mixing of the air within the space (i.e.,
mixing factor = 1). However, perfect mixing usually does not occur, and
the mixing factor could be as high as 10 if air distribution is very poor
(98). The required time is derived by multiplying the appropriate time
from the tale by the mixing factor that has been determined for the booth
or room. The factor and required time should be included in the operating
instructions provided by the manufacturer of the booth or enclosure, and
these instructions should be followed.
2. Exterior devices
The exterior type of local exhaust ventilation device is usually a hood
very near, but not enclosing, the infectious patient. The airflow produced
by these devices should be sufficient to prevent cross-currents of air
near the patient's face from causing escape of droplet nuclei. Whenever
possible, the patient should face directly into the hood opening so that
any coughing or sneezing is directed into the hood, where the droplet nuclei
are captured. The device should maintain an air velocity of greater than
or equal to 200 feet per minute at the patient's breathing zone to ensure
capture of droplet nuclei.
3. Discharge exhaust from booths, tents, and hoods
Air from booths, tents, and hoods may be discharged into the room in
which the device is located or it may be exhausted to the outside. If the
air is discharged into the room, a HEPA filter should be incorporated at
the discharge duct or vent of the device. The exhaust fan should be located
on the discharge side of the HEPA filter to ensure that the air pressure
in the filter housing and booth is negative with respect to adjacent areas.
Uncontaminated air from the room will flow into the booth through all openings,
thus preventing infectious droplet nuclei in the booth from escaping into
the room. Most commercially available booths, tents, and hoods are fitted
with HEPA filters, in which case additional HEPA filtration is not needed.
If the device does not incorporate a HEPA filter, the air from the device
should be exhausted to the outside in accordance with recommendations for
isolation room exhaust (Suppl. 3, Section II.B.5). (See Supplement 3, Section
II.C, for information regarding recirculation of exhaust air.)
B. General Ventilation
General ventilation can be used for several purposes, including diluting
and removing contaminated air, controlling airflow patterns within rooms,
and controlling the direction of airflow throughout a facility. Information
on these topics is contained in the following sections.
1. Dilution and removal
Purpose: To reduce the concentration of contaminants in the air.
General ventilation maintains air quality by two processes: dilution
and removal of airborne contaminants. Uncontaminated supply (i.e., incoming)
air mixes with the contaminated room air (i.e., dilution), which is subsequently
removed from the room by the exhaust system (i.e., removal). These processes
reduce the concentration of droplet nuclei in the room air.
a. Types of general ventilation systems
Two types of general ventilation systems can be used for dilution and
removal of contaminated air: the single-pass system and the recirculating
system. In a single-pass system, the supply air is either outside air that
has been appropriately heated and cooled or air from a central system that
supplies a number of areas. After air passes through the room (or area),
100% of that air is exhausted to the outside. The single-pass system is
the preferred choice in areas where infectious airborne droplet nuclei
are known to be present (e.g., TB isolation rooms or treatment rooms) because
it prevents contaminated air from being recirculated to other areas of
the facility.
In a recirculating system, a small portion of the exhaust air is discharged
to the outside and is replaced with fresh outside air, which mixes with
the portion of exhaust air that was not discharged to the outside. The
resulting mixture, which can contain a large proportion of contaminated
air, is then recirculated to the areas serviced by the system. This air
mixture could be recirculated into the general ventilation, in which case
contaminants may be carried from contaminated areas to uncontaminated areas.
Alternatively, the air mixture could also be recirculated within a specific
room or area, in which case other areas of the facility will not be affected
(Suppl. 3, Section II.C.3).
b. Ventilation rates
Recommended general ventilation rates for health-care facilities are
usually expressed in number of ACH. This number is the ratio of the volume
of air entering the room per hour to the room volume and is equal to the
exhaust airflow (Q [cubic feet per minute]) divided by the room volume
(V [cubic feet]) multiplied by 60 (i.e., ACH = Q / V x 60).
The feasibility of achieving specific ventilation rates depends on the
construction and operational requirements of the ventilation system (e.g.,
the energy requirements to move and to heat or cool the air). The feasibility
of achieving specific ventilation rates may also be different for retrofitted
facilities and newly constructed facilities. The expense and effort of
achieving specific higher ventilation rates for new construction may be
reasonable, whereas retrofitting an existing facility to achieve similar
ventilation rates may be more difficult. However, achieving higher ventilation
rates by using auxiliary methods (e.g., room-air recirculation) in addition
to exhaust ventilation may be feasible in existing facilities (Suppl. 3,
Section II.C).
2. Airflow patterns within rooms (air mixing)
Purpose: To provide optimum airflow patterns and prevent both stagnation
and short-circuiting of air.
General ventilation systems should be designed to provide optimal patterns
of airflow within rooms and prevent air stagnation or short-circuiting
of air from the supply to the exhaust (i.e., passage of air directly from
the air supply to the air exhaust). To provide optimal airflow patterns,
the air supply and exhaust should be located such that clean air first
flows to parts of the room where HCWs are likely to work, and then flows
across the infectious source and into the exhaust. In this way, the HCW
is not positioned between the infectious source and the exhaust location.
Although this configuration may not always be possible, it should be used
whenever feasible. One way to achieve this airflow pattern is to supply
air at the side of the room opposite the patient and exhaust it from the
side where the patient is located. Another method, which is most effective
when the supply air is cooler than the room air, is to supply air near
the ceiling and exhaust it near the floor (Figure S3-2). Airflow patterns
are affected by large air temperature differentials, the precise location
of the supply and exhausts, the location of furniture, the movement of
HCWs and patients, and the physical configuration of the space. Smoke tubes
can be used to visualize airflow patterns in a manner similar to that described
for estimating room air mixing.
Adequate air mixing, which requires that an adequate number of ACH be
provided to a room (Suppl. 3, Section II.B.1), must be ensured to prevent
air stagnation within the room. However, the air will not usually be changed
the calculated number of times per hour because the airflow patterns in
the room may not permit complete mixing of the supply and room air in all
parts of the room. This results in an "effective" airflow rate in which
the supplied airflow may be less than required for proper ventilation.
To account for this variation, a mixing factor (which ranges from 1 for
perfect mixing to 10 for poor mixing) is applied as a multiplier to determine
the actual supply airflow (i.e., the recommended ACH multiplied by the
mixing factor equals the actual required ACH) (51,98). The room air supply
and exhaust system should be designed to achieve the lowest mixing factor
possible. The mixing factor is determined most accurately by experimentally
testing each space configuration, but this procedure is complex and time-consuming.
A reasonably good qualitative measure of mixing can be estimated by an
experienced ventilation engineer who releases smoke from smoke tubes at
a number of locations in the room and observes the movement of the smoke.
Smoke movement in all areas of the room indicates good mixing. Stagnation
of air in some areas of the room indicates poor mixing, and movement of
the supply and exhaust openings or redirection of the supply air is necessary.
(For Figure S3-2, see printed copy)
3. Airflow direction in the facility
Purpose: To contain contaminated air in localized areas in a facility
and prevent its spread to uncontaminated areas.
a. Directional airflow
The general ventilation system should be designed and balanced so that
air flows from less contaminated (i.e., more clean) to more contaminated
(less clean) areas (47,48). For example, air should flow from corridors
(cleaner areas) into TB isolation rooms (less clean areas) to prevent spread
of contaminants to other areas. In some special treatment rooms in which
operative and invasive procedures are performed, the direction of airflow
is from the room to the hallway to provide cleaner air during these procedures.
Cough-inducing or aerosol-generating procedures (e.g., bronchoscopy and
irrigation of tuberculous abscesses) should not be performed in rooms with
this type of airflow on patients who may have infectious TB.
b. Negative pressure for achieving directional airflow
The direction of airflow is controlled by creating a lower (negative)
pressure in the area into which the flow of air is desired. For air to
flow from one area to another, the air pressure in the two areas must be
different. Air will flow from a higher pressure area to a lower pressure
area. The lower pressure area is described as being at negative* pressure
relative to the higher pressure area. Negative pressure is attained by
exhausting air from an area at a higher rate than air is being supplied.
The level of negative pressure necessary to achieve the desired airflow
will depend on the physical configuration of the ventilation system and
area, including the airflow path and flow openings, and should be determined
on an individual basis by an experienced ventilation engineer.
__________ * Negative is defined relative to the air pressure in the
area from which air is to flow.
4. Achieving negative pressure in a room
Purpose: To control the direction of airflow between the room and adjacent
areas, thereby preventing contaminated air from escaping from the room
into other areas of the facility.
a. Pressure differential
The minimum pressure difference necessary to achieve and maintain negative
pressure that will result in airflow into the room is very small (0.001
inch of water). Higher pressures ( greater than or equal to 0.001 inch
of water) are satisfactory; however, these higher pressures may be difficult
to achieve. The actual level of negative pressure achieved will depend
on the difference in the ventilation exhaust and supply flows and the physical
configuration of the room, including the airflow path and flow openings.
If the room is well sealed, negative pressures greater than the minimum
of 0.001 inch of water may be readily achieved. However, if rooms are not
well sealed, as may be the case in many facilities (especially older facilities),
achieving higher negative pressures may require exhaust/supply flow differentials
beyond the capability of the ventilation system.
To establish negative pressure in a room that has a normally functioning
ventilation system, the room supply and exhaust airflows are first balanced
to achieve an exhaust flow of either 10% or 50 cubic feet per minute (cfm)
greater than the supply (whichever is the greater). In most situations,
this specification should achieve a negative pressure of at least 0.001
inch of water. If the minimum 0.001 inch of water is not achieved and cannot
be achieved by increasing the flow differential (within the limits of the
ventilation system), the room should be inspected for leakage (e.g., through
doors, windows, plumbing, and equipment wall penetrations), and corrective
action should be taken to seal the leaks.
Negative pressure in a room can be altered by changing the ventilation
system operation or by the opening and closing of the room's doors, corridor
doors, or windows. When an operating configuration has been established,
it is essential that all doors and windows remain properly closed in the
isolation room and other areas (e.g., doors in corridors that affect air
pressure) except when persons need to enter or leave the room or area.
b. Alternate methods for achieving negative pressure
Although an anteroom is not a substitute for negative pressure in a
room, it may be used to reduce escape of droplet nuclei during opening
and closing of the isolation room door. Some anterooms have their own air
supply duct, but others do not. The TB isolation room should have negative
pressure relative to the anteroom, but the air pressure in the anteroom
relative to the corridor may vary depending on the building design. This
should be determined, in accordance with applicable regulations, by a qualified
ventilation engineer.
If the existing ventilation system is incapable of achieving the desired
negative pressure because the room lacks a separate ventilation system
or the room's system cannot provide the proper airflow, steps should be
taken to provide a means to discharge air from the room. The amount of
air to be exhausted will be the same as discussed previously (Suppl. 3,
Section II.B.4.a).
Fixed room-air recirculation systems (i.e., systems that recirculate
the air in an entire room) may be designed to achieve negative pressure
by discharging air outside the room (Suppl. 3, Section II.C.3).
Some portable room-air recirculation units (Suppl. 3, Section II.C.3.b.)
are designed to discharge air to the outside to achieve negative pressure.
Air cleaners that can accomplish this must be designed specifically for
this purpose.
A small centrifugal blower (i.e., exhaust fan) can be used to exhaust
air to the outside through a window or outside wall. This approach may
be used as an interim measure to achieve negative pressure, but it provides
no fresh air and suboptimal dilution.
Another approach to achieving the required pressure difference is to
pressurize the corridor. Using this method, the corridor's general ventilation
system is balanced to create a higher air pressure in the corridor than
in the isolation room; the type of balancing necessary depends on the configuration
of the ventilation system. Ideally, the corridor air supply rate should
be increased while the corridor exhaust rate is not increased. If this
is not possible, the exhaust rate should be decreased by resetting appropriate
exhaust dampers. Caution should be exercised, however, to ensure that the
exhaust rate is not reduced below acceptable levels. This approach requires
that all settings used to achieve the pressure balance, including doors,
be maintained. This method may not be desirable if the corridor being pressurized
has rooms in which negative pressure is not desired. In many situations,
this system is difficult to achieve, and it should be considered only after
careful review by ventilation personnel.
c. Monitoring negative pressure
The negative pressure in a room can be monitored by visually observing
the direction of airflow (e.g., using smoke tubes) or by measuring the
differential pressure between the room and its surrounding area.
Smoke from a smoke tube can be used to observe airflow between areas
or airflow patterns within an area. To check the negative pressure in a
room by using a smoke tube, hold the smoke tube near the bottom of the
door and approximately 2 inches in front of the door, or at the face of
a grille or other opening if the door has such a feature, and generate
a small amount of smoke by gently squeezing the bulb (Figure S3-3). The
smoke tube should be held parallel to the door, and the smoke should be
issued from the tube slowly to ensure the velocity of the smoke from the
tube does not overpower the air velocity. The smoke will travel in the
direction of airflow. If the room is at negative pressure, the smoke will
travel under the door and into the room (e.g., from higher to lower pressure).
If the room is not at negative pressure, the smoke will be blown outward
or will stay stationary. This test must be performed while the door is
closed. If room air cleaners are being used in the room, they should be
running. The smoke is irritating if inhaled, and care should be taken not
to inhale it directly from the smoke tube. However, the quantity of smoke
issued from the tube is minimal and is not detectable at short distances
from the tube.
Differential pressure-sensing devices also can be used to monitor negative
pressure; they can provide either periodic (noncontinuous) pressure measurements
or continuous pressure monitoring. The continuous monitoring component
may simply be a visible and/or audible warning signal that air pressure
is low. In addition, it may also provide a pressure readout signal, which
can be recorded for later verification or used to automatically adjust
the facility's ventilation control system.
Pressure-measuring devices should sense the room pressure just inside
the airflow path into the room (e.g., at the bottom of the door). Unusual
airflow patterns within the room can cause pressure variations; for example,
the air can be at negative pressure at the middle of a door and at positive
pressure at the bottom of the same door (Figure S-34). If the pressure-sensing
ports of the device cannot be located directly across the airflow path,
it will be necessary to validate that the negative pressure at the sensing
point is and remains the same as the negative pressure across the flow
path.
(For Figure S3-3, see printed copy)
Pressure-sensing devices should incorporate an audible warning with
a time delay to indicate that a door is open. When the door to the room
is opened, the negative pressure will decrease. The time-delayed signal
should allow sufficient time for persons to enter or leave the room without
activating the audible warning.
A potential problem with using pressure-sensing devices is that the
pressure differentials used to achieve the low negative pressure necessitate
the use of very sensitive mechanical devices, electronic devices, or pressure
gauges to ensure accurate measurements. Use of devices that cannot measure
these low pressures (i.e., pressures as low as 0.001 inch of water) will
require setting higher negative pressures that may be difficult and, in
some instances, impractical to achieve (Suppl. 3, Section II.B.4).
Periodic checks are required to ensure that the desired negative pressure
is present and that the continuous monitoring devices, if used, are operating
properly. If smoke tubes or other visual checks are used, TB isolation
rooms and treatment rooms should be checked frequently for negative pressure.
Rooms undergoing changes to the ventilation system should be checked daily.
TB isolation rooms should be checked daily for negative pressure while
being used for TB isolation. If these rooms are not being used for patients
who have suspected or confirmed TB but potentially could be used for such
patients, the negative pressure in the rooms should be checked monthly.
If pressure-sensing devices are used, negative pressure should be verified
at least once a month by using smoke tubes or taking pressure measurements.
(For Figure S3-4, see printed copy)
C. HEPA filtration
Purpose: To remove contaminants from the air.
HEPA filtration can be used as a method of air cleaning that supplements
other recommended ventilation measures. For the purposes of these guidelines,
HEPA filters are defined as air-cleaning devices that have a demonstrated
and documented minimum removal efficiency of 99.97% of particles greater
than or equal to 0.3 um in diameter. HEPA filters have been shown to be
effective in reducing the concentration of Aspergillus spores (which range
in size from 1.5 um to 6 um) to below measurable levels (100-102). The
ability of HEPA filters to remove tubercle bacilli from the air has not
been studied, but M. tuberculosis droplet nuclei probably range from 1
um to 5 um in diameter (i.e., approximately the same size as Aspergillus
spores). Therefore, HEPA filters can be expected to remove infectious droplet
nuclei from contaminated air. HEPA filters can be used to clean air before
it is exhausted to the outside, recirculated to other areas of a facility,
or recirculated within a room. If the device is not completely passive
(e.g., it utilizes techniques such as electrostatics) and the failure of
the electrostatic components permits loss of filtration efficiency to less
than 99.97%, the device should not be used in systems that recirculate
air back into the general facility ventilation system from TB isolation
rooms and treatment rooms in which procedures are performed on patients
who may have infectious TB (Suppl. 3, Section II.C.2).
HEPA filters can be used in a number of ways to reduce or eliminate
infectious droplet nuclei from room air or exhaust. These methods include
placement of HEPA filters a) in exhaust ducts to remove droplet nuclei
from air being discharged to the outside, either directly or through ventilation
equipment; b) in ducts discharging room air into the general ventilation
system; and c) in fixed or portable room-air cleaners. The effectiveness
of portable HEPA room-air cleaning units has not been evaluated adequately,
and there is probably considerable variation in their effectiveness. HEPA
filters can also be used in exhaust ducts or vents that discharge air from
booths or enclosures into the surrounding room (Suppl. 3, Section II.A.3).
In any application, HEPA filters should be installed carefully and maintained
meticulously to ensure adequate function.
Manufacturers of room-air cleaning equipment should provide documentation
of the HEPA filter efficiency and the efficiency of the installed device
in lowering room-air contaminant levels.
1. Use of HEPA filtration when exhausting air to the outside
HEPA filters can be used as an added safety measure to clean air from
isolation rooms and local exhaust devices (i.e., booths, tents, or hoods
used for cough-inducing procedures) before exhausting it directly to the
outside, but such use is unnecessary if the exhaust air cannot re-enter
the ventilation system supply. The use of HEPA filters should be considered
wherever exhaust air could possibly reenter the system.
In many instances, exhaust air is not discharged directly to the outside;
rather, the air is directed through heat-recovery devices (e.g., heat wheels).
Heat wheels are often used to reduce the costs of operating ventilation
systems (103). If such units are used with the system, a HEPA filter should
also be used. As the wheel rotates, energy is transferred into or removed
from the supply inlet air stream. The HEPA filter should be placed upstream
from the heat wheel because of the potential for leakage across the seals
separating the inlet and exhaust chambers and the theoretical possibility
that droplet nuclei could be impacted on the wheel by the exhaust air and
subsequently stripped off into the supply air.
2. Recirculation of HEPA-filtered air to other areas of a facility
Air from TB isolation rooms and treatment rooms used to treat patients
who have confirmed or suspected infectious TB should be exhausted to the
outside in accordance with applicable federal, state, and local regulations.
The air should not be recirculated into the general ventilation. In some
instances, recirculation of air into the general ventilation system from
such rooms is unavoidable (i.e., in existing facilities in which the ventilation
system or facility configuration makes venting the exhaust to the outside
impossible). In such cases, HEPA filters should be installed in the exhaust
duct leading from the room to the general ventilation system to remove
infectious organisms and particulates the size of droplet nuclei from the
air before it is returned to the general ventilation system (Section II.F;
Suppl. 3). Air from TB isolation rooms and treatment rooms in new or renovated
facilities should not be recirculated into the general ventilation system.
3. Recirculation of HEPA-filtered air within a room
Individual room-air recirculation can be used in areas where there is
no general ventilation system, where an existing system is incapable of
providing adequate airflow, or where an increase in ventilation is desired
without affecting the fresh air supply or negative pressure system already
in place. Recirculation of HEPA-filtered air within a room can be achieved
in several ways: a) by exhausting air from the room into a duct, filtering
it through a HEPA filter installed in the duct, and returning it to the
room (Figure S3-5); b) by filtering air through HEPA recirculation systems
mounted on the wall or ceiling of the room (Figure S3-6); or c) by filtering
air through portable HEPA recirculation systems. In this document, the
first two of these approaches are referred to as fixed room-air recirculation
systems, because the HEPA filter devices are fixed in place and are not
easily movable.
(For Figure S3-5, see printed copy)
(For Figure S3-6, see printed copy)
a. Fixed room-air recirculation systems
The preferred method of recirculating HEPA-filtered air within a room
is a built-in system, in which air is exhausted from the room into a duct,
filtered through a HEPA filter, and returned to the room (Figure S3-5).
This technique may be used to add air changes in areas where there is a
recommended minimum ACH that is difficult to meet with general ventilation
alone. The air does not have to be conditioned, other than by the filtration,
and this permits higher airflow rates than the general ventilation system
can usually achieve. An alternative is the use of HEPA filtration units
that are mounted on the wall or ceiling of the room (Figure S3-7). Fixed
recirculation systems are preferred over portable (free-standing) units
because they can be installed and maintained with a greater degree of reliability.
b. Portable room-air recirculation units
Portable HEPA filtration units may be considered for recirculating air
within rooms in which there is no general ventilation system, where the
system is incapable of providing adequate airflow, or where increased effectiveness
in room airflow is desired. Effectiveness depends on circulating as much
of the air in the room as possible through the HEPA filter, which may be
difficult to achieve and evaluate. The effectiveness of a particular unit
can vary depending on the room's configuration, the furniture and persons
in the room, and placement of the HEPA filtration unit and the supply and
exhaust grilles. Therefore, the effectiveness of the portable unit may
vary considerably in rooms with different configurations or in the same
room if moved from one location to another in the room. If portable units
are used, caution should be exercised to ensure they can recirculate all
or nearly all of the room air through the HEPA filter. Some commercially
available units may not be able to meet this requirement because of design
limitations or insufficient airflow capacity. In addition, units should
be designed and operated to ensure that persons in the room cannot interfere
with or otherwise compromise the functioning of the unit. Portable HEPA
filtration units have not been evaluated adequately to determine their
role in TB infection-control programs.
Portable HEPA filtration units should be designed to achieve the equivalent
of greater than or equal to 12 ACH. They should also be designed to ensure
adequate air mixing in all areas of the hospital rooms in which they are
used, and they should not interfere with the current ventilation system.
Some HEPA filtration units employ UVGI for disinfecting air after HEPA
filtration. However, whether exposing the HEPA-filtered air to UV irradiation
further decreases the concentration of contaminants is not known.
c. Evaluation of room-air recirculation systems and units
Detailed and accurate evaluations of room-air recirculation systems
and units require the use of sophisticated test equipment and lengthy test
procedures that are not practical. However, an estimate of the unit's ability
to circulate the air in the room can be made by visualizing airflow patterns
as was described previously for estimating room air mixing (Suppl. 3, Section
II.B.1). If the air movement is good in all areas of the room, the unit
should be effective.
4. Installing, maintaining, and monitoring HEPA filters
Proper installation and testing and meticulous maintenance are critical
if a HEPA filtration system is used (104), especially if the system used
recirculates air to other parts of the facility. Improper design, installation,
or maintenance could allow infectious particles to circumvent filtration
and escape into the general ventilation system (47). HEPA filters should
be installed to prevent leakage between filter segments and between the
filter bed and its frame. A regularly scheduled maintenance program is
required to monitor the HEPA filter for possible leakage and for filter
loading. A quantitative leakage and filter performance test (e.g., the
dioctal phthalate [DOP] penetration test [105]) should be performed at
the initial installation and every time the filter is changed or moved.
The test should be repeated every 6 months for filters in general-use areas
and in areas with systems that exhaust air that is likely to be contaminated
with M. tuberculosis (e.g, TB isolation rooms).
A manometer or other pressure-sensing device should be installed in
the filter system to provide an accurate and objective means of determining
the need for filter replacement. Pressure drop characteristics of the filter
are supplied by the manufacturer of the filter. Installation of the filter
should allow for maintenance that will not contaminate the delivery system
or the area served. For general infection-control purposes, special care
should be taken to not jar or drop the filter element during or after removal.
The scheduled maintenance program should include procedures for installation,
removal, and disposal of filter elements. HEPA filter maintenance should
be performed only by adequately trained personnel. Appropriate respiratory
protection should be worn while performing maintenance and testing procedures.
In addition, filter housing and ducts leading to the housing should be
labelled clearly with the words "Contaminated Air" (or a similar warning).
When a HEPA filter is used, one or more lower efficiency disposable
prefilters installed upstream will extend the useful life of the HEPA filter.
A disposable filter can increase the life of a HEPA filter by 25%. If the
disposable filter is followed by a 90% extended surface filter, the life
of the HEPA filter can be extended almost 900% (98). These prefilters should
be handled and disposed of in the same manner as the HEPA filter.
D. TB Isolation Rooms and Treatment Rooms
Purpose: To separate patients who are likely to have infectious TB from
other persons, to provide an environment that will allow reduction of the
concentration of droplet nuclei through various engineering methods, and
to prevent the escape of droplet nuclei from such rooms into the corridor
and other areas of the facility using directional airflow.
A hierarchy of ventilation methods used to achieve a reduction in the
concentration of droplet nuclei and to achieve directional airflow using
negative pressure has been developed (Table S3-2). The methods are listed
in order from the most desirable to the least desirable. The method selected
will depend on the configuration of the isolation room and the ventilation
system in the facility; the determination should be made in consultation
with a ventilation engineer.
(For Table S3-2, see printed copy)
1. Preventing the escape of droplet nuclei from the room
Rooms used for TB isolation should be single-patient rooms with negative
pressure relative to the corridor or other areas connected to the room.
Doors between the isolation room and other areas should remain closed except
for entry into or exit from the room. The room's openings (e.g., windows
and electrical and plumbing entries) should be sealed as much as possible.
However, a small gap of 1/8 to 1/2 inch should be at the bottom of the
door to provide a controlled airflow path. Proper use of negative pressure
will prevent contaminated air from escaping the room.
2. Reducing the concentration of droplet nuclei in the room
ASHRAE (47), AIA (48), and the Health Resources and Services Administration
(49) recommend a minimum of 6 ACH for TB isolation rooms and treatment
rooms. This ventilation rate is based on comfort- and odor-control considerations.
The effectiveness of this level of airflow in reducing the concentration
of droplet nuclei in the room, thus reducing the transmission of airborne
pathogens, has not been evaluated directly or adequately.
Ventilation rates greater than 6 ACH are likely to produce an incrementally
greater reduction in the concentration of bacteria in a room than are lower
rates (50-52). However, accurate quantitation of decreases in risk that
would result from specific increases in general ventilation levels has
not been performed and may not be possible.
To reduce the concentration of droplet nuclei, TB isolation rooms and
treatment rooms in existing health-care facilities should have an airflow
of greater than or equal to 6 ACH. Where feasible, this airflow rate should
be increased to greater than or equal to 12 ACH by adjusting or modifying
the ventilation system or by using auxiliary means (e.g., recirculation
of air through fixed HEPA filtration units or portable air cleaners) (Suppl.
3, Section II.C) (53). New construction or renovation of existing health-care
facilities should be designed so that TB isolation rooms achieve an airflow
of greater than or equal to 12 ACH.
3. Exhaust from TB isolation rooms and treatment rooms
Air from TB isolation rooms and treatment rooms in which patients with
infectious TB may be examined should be exhausted directly to the outside
of the building and away from air-intake vents, persons, and animals in
accordance with federal, state, and local regulations concerning environmental
discharges. (See Suppl. 3, Section II.C, for information regarding recirculation
of exhaust air.) Exhaust ducts should not be located near areas that may
be populated (e.g., near sidewalks or windows that could be opened). Ventilation
system exhaust discharges and inlets should be designed to prevent reentry
of exhausted air. Wind blowing over a building creates a highly turbulent
recirculation zone, which can cause exhausted air to reenter the building
(Figure S3-7). Exhaust flow should be discharged above this zone (Suppl.
3, Section II.C.1). Design guidelines for proper placement of exhaust ducts
can be found in the 1989 ASHRAE Fundamentals Handbook (106). If recirculation
of air from such rooms into the general ventilation system is unavoidable,
the air should be passed through a HEPA filter before recirculation (Suppl.
3, Section II.C.2).
4. Alternatives to TB isolation rooms
Isolation can also be achieved by use of negative-pressure enclosures
(e.g, tents or booths) (Suppl. 3, Section II.A.1). These can be used to
provide patient isolation in areas such as emergency rooms and medical
testing and treatment areas and to supplement isolation in designated isolation
rooms.
III. UVGI
Purpose: To kill or inactivate airborne tubercle bacilli.
Research has demonstrated that UVGI is effective in killing or inactivating
tubercle bacilli under experimental conditions (66,107-110) and in reducing
transmission of other infections in hospitals (111), military housing (112),
and classrooms (113-115). Because of the results of numerous studies (116-120)
and the experiences of TB clinicians and mycobacteriologists during the
past several decades, the use of UVGI has been recommended as a supplement
to other TB infection-control measures in settings where the need for killing
or inactivating tubercle bacilli is important (2,4,121-125).
(For Figure S3-7, see printed copy)
UV radiation is defined as that portion of the electromagnetic spectrum
described by wavelengths from 100 to 400 nm. For convenience of classification,
the UV spectrum has been separated into three different wave-length bands:
UV-A (long wavelengths, range: 320-400 nm), UV-B (midrange wavelengths,
range: 290-320 nm), and UV-C (short wavelengths, range: 100-290 nm) (126).
Commercially available UV lamps used for germicidal purposes are low-pressure
mercury vapor lamps (127) that emit radiant energy in the UV-C range, predominantly
at a wavelength of 253.7 nm (128).
A. Applications
UVGI can be used as a method of air disinfection to supplement other
engineering controls. Two systems of UVGI can be used for this purpose:
duct irradiation and upper-room air irradiation.
1. Duct irradiation
Purpose: To inactivate tubercle bacilli without exposing persons to
UVGI.
In duct irradiation systems, UV lamps are placed inside ducts that remove
air from rooms to disinfect the air before it is recirculated. When UVGI
duct systems are properly designed, installed, and maintained, high levels
of UV radiation may be produced in the duct work. The only potential for
human exposure to this radiation occurs during maintenance operations.
Duct irradiation may be used:
* In a TB isolation room or treatment room to recirculate air from the
room, through a duct containing UV lamps, and back into the room. This
recirculation method can increase the overall room airflow but does not
increase the supply of fresh outside air to the room.
* In other patients' rooms and in waiting rooms, emergency rooms, and
other general-use areas of a facility where patients with undiagnosed TB
could potentially contaminate the air, to recirculate air back into the
general ventilation.
Duct-irradiation systems are dependent on airflow patterns within a
room that ensure that all or nearly all of the room air circulates through
the duct.
2. Upper-room air irradiation
Purpose: To inactivate tubercle bacilli in the upper part of the room,
while minimizing radiation exposure to persons in the lower part of the
room.
In upper-room air irradiation, UVGI lamps are suspended from the ceiling
or mounted on the wall. The bottom of the lamp is shielded to direct the
radiation upward but not downward. The system depends on air mixing to
take irradiated air from the upper to the lower part of the room, and nonirradiated
air from the lower to the upper part. The irradiated air space is much
larger than that in a duct system.
UVGI has been effective in killing bacteria under conditions where air
mixing was accomplished mainly by convection. For example, BCG was atomized
in a room that did not have supplemental ventilation (120), and in another
study a surrogate bacteria, Serratia marcesens, was aerosolized in a room
with a ventilation rate of 6 ACH (129). These reports estimated the effect
of UVGI to be equivalent to 10 and 39 ACH, respectively, for the organisms
tested, which are less resistant to UVGI than M. tuberculosis (120). The
addition of fans or some heating/air conditioning arrangements may double
the effectiveness of UVGI lamps (130-132). Greater rates of ventilation,
however, may decrease the length of time the air is irradiated, thus decreasing
the killing of bacteria (117,129). The optimal relationship between ventilation
and UVGI is not known. Air irradiation lamps used in corridors have been
effective in killing atomized S. marcesens (133). Use of UVGI lamps in
an outpatient room has reduced culturable airborne bacteria by 14%-19%.
However, the irradiation did not reduce the concentration of gram-positive,
rod-shaped bacteria; although fast-growing mycobacteria were cultured,
M. tuberculosis could not be recovered from the room's air samples because
of fungal over-growth of media plates (134).
Upper-room air UVGI irradiation may be used:
* In isolation or treatment rooms as a supplemental method of air cleaning.
* In other patients' rooms and in waiting rooms, emergency rooms, corridors,
and other central areas of a facility where patients with undiagnosed TB
could potentially contaminate the air.
Determinants of UVGI effectiveness include room configuration, UV lamp
placement, and the adequacy of airflow patterns in bringing contaminated
air into contact with the irradiated upper-room space. Air mixing may be
facilitated by supplying cool air near the ceiling in rooms where warmer
air (or a heating device) is present below. The ceiling should be high
enough for a large volume of upper-room air to be irradiated without HCWs
and patients being overexposed to UV radiation.
B. Limitations
Because the clinical effectiveness of UV systems varies, and because
of the risk for transmission of M. tuberculosis if a system malfunctions
or is maintained improperly, UVGI is not recommended for the following
specific applications:
1. Duct systems using UVGI are not recommended as a substitute for HEPA
filters if air from isolation rooms must be recirculated to other areas
of a facility.
2. UVGI alone is not recommended as a substitute for HEPA filtration
or local exhaust of air to the outside from booths, tents, or hoods used
for cough-inducing procedures.
3. UVGI is not a substitute for negative pressure.
The use of UV lamps and HEPA filtration in a single unit would not be
expected to have any infection-control benefits not provided by use of
the HEPA filter alone.
The effectiveness of UVGI in killing airborne tubercle bacilli depends
on the intensity of UVGI, the duration of contact the organism has with
the irradiation, and the relative humidity (66,108,111). Humidity can have
an adverse effect on UVGI effectiveness at levels greater than 70% relative
humidity for S. marcescens (135). The interaction of these factors has
not been fully defined, however, making precise recommendations for individual
UVGI installations difficult to develop.
Old lamps or dust-covered UV lamps are less effective; therefore, regular
maintenance of UVGI systems is crucial.
C. Safety Issues
Short-term overexposure to UV radiation can cause erythema and keratoconjunctivitis
(136,137). Broad-spectrum UV radiation has been associated with increased
risk for squamous and basal cell carcinomas of the skin (138). UV-C was
recently classified by the International Agency for Research on Cancer
as "probably carcinogenic to humans (Group 2A)" (138). This classification
is based on studies suggesting that UV-C radiation can induce skin cancers
in animals; DNA damage, chromosomal aberrations and sister chromatid exchange
and transformation in human cells in vitro; and DNA damage in mammalian
skin cells in vivo. In the animal studies, a contribution of UV-B to the
tumor effects could not be excluded, but the effects were greater than
expected for UV-B alone (138). Although some recent studies have demonstrated
that UV radiation can activate HIV gene promoters (i.e., the genes in HIV
that prompt replication of the virus) in laboratory samples of human cells
(139-144), the implications of these in vitro findings for humans are unknown.
In 1972, the National Institute for Occupational Safety and Health (NIOSH)
published a recommended exposure limit (REL) for occupational exposure
to UV radiation (136). The REL is intended to protect workers from the
acute effects of UV exposure (e.g., erythema and photokeratoconjunctivitis).
However, photosensitive persons and those exposed concomitantly to photoactive
chemicals may not be protected by the recommended standard.
If proper procedures are not followed, HCWs performing maintenance on
such fixtures are at risk for exposure to UV radiation. Because UV fixtures
used for upper-room air irradiation are present in rooms, rather than hidden
in ducts, safety may be much more difficult to achieve and maintain. Fixtures
must be designed and installed to ensure that UV exposure to persons in
the room (including HCWs and inpatients) are below current safe exposure
levels. Recent health hazard evaluations conducted by CDC have noted problems
withover-exposure of HCWs to UVGI and with inadequate maintenance, training,
labelling, and use of personal protective equipment (145-147).
The current number of persons who are properly trained in UVGI system
design and installation is limited. CDC strongly recommends that a competent
UVGI system designer be consulted to address safety considerations before
such a system is procured and installed. Experts who might be consulted
include industrial hygienists, engineers, and health physicists. Principles
for the safe installation of UV lamp fixtures have been developed and can
be used as guidelines (148,149).
If UV lamps are being used in a facility, the general TB education of
HCWs should include:
1. The basic principles of UVGI systems (i.e., how they work and what
their limitations are).
2. The potential hazardous effects of UVGI if overexposure occurs.
3. The potential for photosensitivity associated with certain medical
conditions or use of some medications.
4. The importance of general maintenance procedures for UVGI fixtures.
Exposure to UV intensities above the REL should be avoided. Lightweight
clothing made of tightly woven fabric and UV-absorbing sunscreens with
solar-protection factors (SPFs) greater than or equal to 15 may help protect
photosensitive persons. HCWs should be advised that any eye or skin irritation
that develops after UV exposure should be examined by occupational health
staff.
D. Exposure Criteria for UV Radiation
The NIOSH REL for UV radiation is wavelength dependent because different
wavelengths of UV radiation have different adverse effects on the skin
and eyes (136). Relative spectral effectiveness (S lambda) is used to compare
various UV sources with a source producing UV radiation at 270 nm, the
wavelength of maximum ocular sensitivity. For example, the S lambda at
254 nm is 0.5; therefore, twice as much energy is required at 254 nm to
produce an identical biologic effect at 270 nm (136). Thus, at 254 nm,
the NIOSH REL is 0.006 joules per square centimeter (J/cm(2)); and at 270
nm, it is 0.003 J/cm(2).
For germicidal lamps that emit radiant energy predominantly at a wavelength
of 254 nm, proper use of the REL requires that the measured irradiance
level (E) in microwatts per square centimeter (uW/cm(2)) be multiplied
by the relative spectral effectiveness at 254 nm (0.5) to obtain the effective
irradiance (E(eff)). The maximum permissible exposure time can then be
determined for selected values of E(eff) (Table S3-3), or it can be calculated
(in seconds) by dividing 0.003 J/cm(2) (the NIOSH REL at 270 nm) by E(eff)
in uW/cm(2) (136,150).
To protect HCWs who are exposed to germicidal UV radiation for 8 hours
per workday, the measured irradiance (E) should be less than or equal to
0.2 uW/cm(2). This is calculated by obtaining If (0.1 uW/cm(2)) (Table
S3-3) and then dividing this value by S lambda (0.5).
E. Maintenance and Monitoring
1. Labelling and posting
Warning signs should be posted on UV lamps and wherever high-intensity
(i.e., UV exposure greater than the REL) germicidal UV irradiation is present
(e.g., upper-room air space and accesses to ducts [if duct irradiation
is used]) to alert maintenance staff or other HCWs of the hazard. Some
examples are shown below:
(For Table S3-3, see printed copy)
______________________ ______________________ | | | | | CAUTION | |
CAUTION | | ULTRAVIOLET ENERGY: | | | |TURN OFF LAMPS BEFORE | | ULTRAVIOLET
ENERGY: | | ENTERING UPPER ROOM | | PROTECT EYES & SKIN | |______________________|
|______________________|
2. Maintenance
Because the intensity of UV lamps fluctuates as they age, a schedule
for replacing the lamps should be developed. The schedule can be determined
from either a time/use log or a system based on cumulative time. The tube
should be checked periodically for dust build-up, which lessens the output
of UVGI. If the tube is dirty, it should be allowed to cool, then cleaned
with a damp cloth. Tubes should be replaced if they stop glowing or if
they flicker to an objectionable extent. Maintenance personnel must turn
off all UV tubes before entering the upper part of the room or before accessing
ducts for any purpose. Only a few seconds of direct exposure to the intense
UV radiation in the upper-room air space or in ducts can cause burns. Protective
equipment (e.g., gloves and goggles [and/or face shields]) should be worn
if exposure greater than the recommended standard is anticipated.
Banks of UVGI tubes can be installed in ventilating ducts. Safety devices
should be used on access doors to eliminate hazard to maintenance personnel.
For duct irradiation systems, the access door for servicing the lamps should
have an inspection window* through which the lamps are checked periodically
for dust build-up and malfunctioning. The access door should have a warning
sign written in languages appropriate for maintenance personnel to alert
them to the health hazard of looking directly at bare tubes. The lock for
this door should have an automatic electric switch or other device that
turns off the lamps when the door is opened.
__________ * Ordinary glass (not quartz) is sufficient to filter out
UV radiation.
Two types of fixtures are used in upper-room air irradiation: wall-mounted
fixtures that have louvers to block downward radiation and ceiling-mounted
fixtures that have baffles to block radiation below the horizontal plane
of the UV tube. The actual UV tube in either type of fixture must not be
visible from any normal position in the room. Light switches that can be
locked should be used, if possible, to prevent injury to personnel who
might unintentionally turn the lamps on during maintenance procedures.
In most applications, properly shielding the UV lamps to provide protection
from most, if not all, of the direct UV radiation is not difficult. However,
radiation reflected from glass, polished metal, and high-gloss ceramic
paints can be harmful to persons in the room, particularly if more than
one UV lamp is in use. Surfaces in irradiated rooms that can reflect UVGI
into occupied areas of the room should be covered with non-UV reflecting
material.
3. Monitoring
A regularly scheduled evaluation of the UV intensity to which HCWs,
patients, and others are exposed should be conducted.
UV measurements should be made in various locations within a room using
a detector designed to be most sensitive at 254 nm. Equipment used to measure
germicidal UV radiation should be maintained and calibrated on a regular
schedule.
A new UV installation must be carefully checked for hot spots (i.e.,
areas of the room where the REL is exceeded) by an industrial hygienist
or other person knowledgeable in making UV measurements. UV radiation levels
should not exceed those in the recommended guidelines.
Supplement 4: Respiratory Protection
I. Considerations for Selection of Respirators
Personal respiratory protection should be used by a) persons entering
rooms where patients with known or suspected infectious TB are being isolated,
b) persons present during cough-inducing or aerosol-generating procedures
performed on such patients, and c) persons in other settings where administrative
and engineering controls are not likely to protect them from inhaling infectious
airborne droplet nuclei. These other settings should be identified on the
basis of the facility's risk assessment.
Although data regarding the effectiveness of respiratory protection
from many hazardous airborne materials have been collected, the precise
level of effectiveness in protecting HCWs from M. tuberculosis transmission
in health-care settings has not been determined. Information concerning
the transmission of M. tuberculosis is incomplete. Neither the smallest
infectious dose of M. tuberculosis nor the highest level of exposure to
M. tuberculosis at which transmission will not occur has been defined conclusively
(59,151,152). Furthermore, the size distribution of droplet nuclei and
the number of particles containing viable M. tuberculosis that are expelled
by infectious TB patients have not been defined adequately, and accurate
methods of measuring the concentration of infectious droplet nuclei in
a room have not been developed.
Nevertheless, in certain settings the administrative and engineering
controls may not adequately protect HCWs from airborne droplet nuclei (e.g.,
in TB isolation rooms, treatment rooms in which cough-inducing or aerosol-generating
procedures are performed, and ambulances during the transport of infectious
TB patients). Respiratory protective devices used in these settings should
have characteristics that are suitable for the organism they are protecting
against and the settings in which they are used.
A. Performance Criteria for Personal Respirators for Protection
Against Transmission of M. tuberculosis
Respiratory protective devices used in health-care settings for protection
against M. tuberculosis should meet the following standard criteria. These
criteria are based on currently available information, including a) data
on the effectiveness of respiratory protection against noninfectious hazardous
materials in workplaces other than health-care settings and on an interpretation
of how these data can be applied to respiratory protection against M. tuberculosis;
b) data on the efficiency of respirator filters in filtering biological
aerosols; c) data on face-seal leakage; and d) data on the characteristics
of respirators that were used in conjunction with administrative and engineering
controls in outbreak settings where transmission to HCWs and patients was
terminated.
1. The ability to filter particles 1 um in size in the unloaded state
with a filter efficiency of greater than or equal to 95% (i.e., filter
leakage of less than or equal to 5%), given flow rates of up to 50 L per
minute.
Available data suggest that infectious droplet nuclei range in size
from 1 um to 5 um; therefore, respirators used in health-care settings
should be able to efficiently filter the smallest particles in this range.
Fifty liters per minute is a reasonable estimate of the highest airflow
rate an HCW is likely to achieve during breathing, even while performing
strenuous work activities.
2. The ability to be qualitatively or quantitatively fit tested in a
reliable way to obtain a face-seal leakage of less than or equal to 10%
(54,55).
3. The ability to fit the different facial sizes and characteristics
of HCWs, which can usually be met by making the respirators available in
at least three sizes.
4. The ability to be checked for facepiece fit, in accordance with OSHA
standards and good industrial hygiene practice, by HCWs each time they
put on their respirators (54,55).
In some settings, HCWs may be at risk for two types of exposure: a)
inhalation of M. tuberculosis and b) mucous membrane exposure to fluids
that may contain bloodborne pathogens. In these settings, protection against
both types of exposure should be used.
When operative procedures (or other procedures requiring a sterile field)
are performed on patients who may have infectious TB, respiratory protection
worn by the HCW should serve two functions: a) it should protect the surgical
field from the respiratory secretions of the HCW and b) it should protect
the HCW from infectious droplet nuclei that may be expelled by the patient
or generated by the procedure. Respirators with expiration valves and positive-pressure
respirators do not protect the sterile field; therefore, a respirator that
does not have a valve and that meets the criteria in Supplement 4, Section
I.A, should be used.
B. Specific Respirators
The OSHA respiratory protection standard requires that all respiratory
protective devices used in the workplace be certified by NIOSH.* NIOSH-approved
HEPA respirators are the only currently available air-purifying respirators
that meet or exceed the standard performance criteria stated above. However,
the NIOSH certification procedures are currently being revised (153). Under
the proposed revision, filter materials would be tested at a flow rate
of 85 L/min for penetration by particles with a median aerodynamic diameter
of 0.3 um and, if certified, would be placed in one of the following categories:
type A, which has greater than or equal to 99.97% efficiency (similar to
current HEPA filter media); type B, greater than or equal to 99% efficiency;
or type C, greater than or equal to 95% efficiency. According to this proposed
scheme, type C filter material would meet or exceed the standard performance
criteria specified in this document.
__________ * 29 CFR Part 1910.134.
The facility's risk assessment may identify a limited number of selected
settings (e.g., bronchoscopy performed on patients suspected of having
TB or autopsy performed on deceased persons suspected of having had active
TB at the time of death) where the estimated risk for transmission of M.
tuberculosis may be such that a level of respiratory protection exceeding
the standard criteria is appropriate. In such circumstances, a level of
respiratory protection exceeding the standard criteria and compatible with
patient-care delivery (e.g., negative-pressure respirators that are more
protective; powered air-purifying particulate respirators [PAPRs]; or positive-pressure
airline, half-mask respirators) should be provided by employers to HCWs
who are exposed to M. tuberculosis. Information on these and other respirators
may be found in the NIOSH Guide to Industrial Respiratory Protection (55).
C. The Effectiveness of Respiratory Protective Devices
The following information, which is based on experience with respiratory
protection in the industrial setting, summarizes the available data about
the effectiveness of respiratory protection against hazardous airborne
materials. Data regarding protection against transmission of M. tuberculosis
are not available.
The parameters used to determine the effectiveness of a respiratory
protective device are face-seal efficacy and filter efficacy.
1. Face-seal leakage
Face-seal leakage compromises the ability of particulate respirators
to protect HCWs from airborne materials (154-156). A proper seal between
the respirator's sealing surface and the face of the person wearing the
respirator is essential for effective and reliable performance of any negative-pressure
respirator. This seal is less critical, but still important, for positive-pressure
respirators. Face-seal leakage can result from various factors, including
incorrect facepiece size or shape, incorrect or defective facepiece sealing-lip,
beard growth, perspiration or facial oils that can cause facepiece slippage,
failure to use all the head straps, incorrect positioning of the facepiece
on the face, incorrect head strap tension or position, improper respirator
maintenance, and respirator damage.
Every time a person wearing a negative-pressure particulate respirator
inhales, a negative pressure (relative to the workplace air) is created
inside the facepiece. Because of this negative pressure, air containing
contaminants can take a path of least resistance into the respirator --
through leaks at the face-seal interface -- thus avoiding the higher-resistance
filter material. Currently available, cup-shaped, disposable particulate
respirators have from 0 to 20% face-seal leakage (55,154). This face-seal
leakage results from the variability of the human face and from limitations
in the respirator's design, construction, and number of sizes available.
The face-seal leakage is probably higher if the respirator is not fitted
properly to the HCW's face, tested for an adequate fit by a qualified person,
and then checked for fit by the HCW every time the respirator is put on.
Face-seal leakage may be reduced to less than 10% with improvements in
design, a greater variety in available sizes, and appropriate fit testing
and fit checking.
In comparison with negative-pressure respirators, positive-pressure
respirators produce a positive pressure inside the facepiece under most
conditions of use. For example, in a PAPR, a blower forcibly draws ambient
air through HEPA filters, then delivers the filtered air to the facepiece.
This air is blown into the facepiece at flow rates that generally exceed
the expected inhalation flow rates. The positive pressure inside the facepiece
reduces face-seal leakage to low levels, particularly during the relatively
low inhalation rates expected in health-care settings. PAPRs with a tight-fitting
facepiece have less than 2% face-seal leakage under routine conditions
(55). Powered-air respirators with loose-fitting facepieces, hoods, or
helmets have less than 4% face-seal leakage under routine conditions (55).
Thus, a PAPR may offer lower levels of face-seal leakage than nonpowered,
half-mask respirators. Full facepiece, nonpowered respirators have the
same leakage (i.e., less than 2%) as PAPRs.
Another factor contributing to face-seal leakage of cup-shaped, disposable
respirators is that some of these respirators are available in only one
size. A single size may produce higher leakage for persons who have smaller
or difficult-to-fit faces (157). The facepieces used for some reusable
(including HEPA and replaceable filter, negative-pressure) and all positive-pressure
particulate air-purifying respirators are available in as many as three
different sizes.
2. Filter leakage
Aerosol leakage through respirator filters depends on at least five
independent variables: a) the filtration characteristics for each type
of filter, b) the size distribution of the droplets in the aerosol, c)
the linear velocity through the filtering material, d) the filter loading
(i.e., the amount of contaminant deposited on the filter), and e) any electrostatic
charges on the filter and on the droplets in the aerosol (158).
When HEPA filters are used in particulate air-purifying respirators,
filter efficiency is so high (i.e., effectively 100%) that filter leakage
is not a consideration. Therefore, for all HEPA-filter respirators, virtually
all inward leakage of droplet nuclei occurs at the respirator's face seal.
3. Fit testing
Fit testing is part of the respiratory protection program required by
OSHA for all respiratory protective devices used in the workplace. A fit
test determines whether a respiratory protective device adequately fits
a particular HCW. The HCW may need to be fit tested with several devices
to determine which device offers the best fit. However, fit tests can detect
only the leakage that occurs at the time of the fit testing, and the tests
cannot distinguish face-seal leakage from filter leakage.
Determination of facepiece fit can involve qualitative or quantitative
tests (55). A qualitative test relies on the subjective response of the
HCW being fit tested. A quantitative test uses detectors to measure inward
leakage.
Disposable, negative-pressure particulate respirators can be qualitatively
fit tested with aerosolized substances that can be tasted, although the
results of this testing are limited because the tests depend on the subjective
response of the HCW being tested. Quantitative fit testing of disposable
negative-pressure particulate respirators can best be performed if the
manufacturer provides a test respirator with a probe for this purpose.
Replaceable filter, negative-pressure particulate respirators and all
positive-pressure particulate respirators can be fit tested reliably, both
qualitatively and quantitatively, when fitted with HEPA filters.
4. Fit checking
A fit check is a maneuver that an HCW performs before each use of the
respiratory protective device to check the fit. The fit check can be performed
according to the manufacturer's facepiece fitting instructions by using
the applicable negative-pressure or positive-pressure test.
Some currently available cup-shaped, disposable negative-pressure particulate
respirators cannot be fit checked reliably by persons wearing the devices
because occluding the entire surface of the filter is difficult. Strategies
for overcoming these limitations are being developed by respirator manufacturers.
5. Reuse of respirators
Conscientious respirator maintenance should be an integral part of an
overall respirator program. This maintenance applies both to respirators
with replaceable filters and respirators that are classified as disposable
but that are reused. Manufacturers' instructions for inspecting, cleaning,
and maintaining respirators should be followed to ensure that the respirator
continues to function properly (55).
When respirators are used for protection against noninfectious aerosols
(e.g., wood dust), which may be present in the air in heavy concentrations,
the filter material may become occluded with airborne material. This occlusion
may result in an uncomfortable breathing resistance. In health-care settings
where respirators are used for protection against biological aerosols,
the concentration of infectious particles in the air is probably low; thus,
the filter material in a respirator is very unlikely to become occluded
with airborne material. In addition, there is no evidence that particles
impacting on the filter material in a respirator are re-aerosolized easily.
For these reasons, the filter material used in respirators in the health-care
setting should remain functional for weeks to months. Respirators with
replaceable filters are reusable, and a respirator classified as disposable
may be reused by the same HCW as long as it remains functional.
Before each use, the outside of the filter material should be inspected.
If the filter material is physically damaged or soiled, the filter should
be changed (in the case of respirators with replaceable filters) or the
respirator discarded (in the case of disposable respirators). Infection-control
personnel should develop standard operating procedures for storing, reusing,
and disposing of respirators that have been designated as disposable and
for disposing of replaceable filter elements.
II. Implementing a Personal Respiratory Protection Program
If personal respiratory protection is used in a health-care setting,
OSHA requires that an effective personal respiratory protection program
be developed, implemented, administered, and periodically reevaluated (54,55).
All HCWs who need to use respirators for protection against infection
with M. tuberculosis should be included in the respiratory protection program.
Visitors to TB patients should be given respirators to wear while in isolation
rooms, and they should be given general instructions on how to use their
respirators.
The number of HCWs included in the respiratory protection program in
each facility will vary depending on a) the number of potentially infectious
TB patients, b) the number of rooms or areas to which patients with suspected
or confirmed infectious TB are admitted, and c) the number of HCWs needed
in these rooms or areas. Where respiratory protection programs are required,
they should include enough HCWs to provide adequate care for a patient
with known or suspected TB should such a patient be admitted to the facility.
However, administrative measures should be used to limit the number of
HCWs who need to enter these rooms or areas, thus limiting the number of
HCWs who need to be included in the respiratory protection program.
Information regarding the development and management of a respiratory
protection program is available in technical training courses that cover
the basics of personal respiratory protection. Such courses are offered
by various organizations, such as NIOSH, OSHA, and the American Industrial
Hygiene Association. Similar courses are available from private contractors
and universities.
To be effective and reliable, respiratory protection programs must contain
at least the following elements (55,154):
1. Assignment of responsibility. Supervisory responsibility for the
respiratory protection program should be assigned to designated persons
who have expertise in issues relevant to the program, including infectious
diseases and occupational health.
2. Standard operating procedures. Written standard operating procedures
should contain information concerning all aspects of the respiratory protection
program.
3. Medical screening. HCWs should not be assigned a task requiring use
of respirators unless they are physically able to perform the task while
wearing the respirator. HCWs should be screened for pertinent medical conditions
at the time they are hired, then rescreened periodically (55). The screening
could occur as infrequently as every 5 years. The screening process should
begin with a general screening (e.g., a questionnaire) for pertinent medical
conditions, and the results of the screening should then be used to identify
HCWs who need further evaluation. Routine physical examination or testing
with chest radiographs or spirometry is not necessary or required.
Few medical conditions preclude the use of most negative-pressure particulate
respirators. HCWs who have mild pulmonary or cardiac conditions may report
discomfort with breathing when wearing negative-pressure particulate respirators,
but these respirators are unlikely to have adverse health effects on the
HCWs. Those HCWs who have more severe cardiac or pulmonary conditions may
have more difficulty than HCWs with similar but milder conditions if performing
duties while wearing negative-pressure respirators. Furthermore, these
HCWs may be unable to use some PAPRs because of the added weight of these
respirators.
4. Training. HCWs who wear respirators and the persons who supervise
them should be informed about the necessity for wearing respirators and
the potential risks associated with not doing so. This training should
also include at a minimum:
* The nature, extent, and specific hazards of M. tuberculosis transmission
in their respective health-care facility.
* A description of specific risks for TB infection among persons exposed
to M. tuberculosis, of any subsequent treatment with INH or other chemoprophylactic
agents, and of the possibility of active TB disease.
* A description of engineering controls and work practices and the reasons
why they do not eliminate the need for personal respiratory protection.
* An explanation for selecting a particular type of respirator, how
the respirator is properly maintained and stored, and the operation, capabilities,
and limitations of the respirator provided.
* Instruction in how the HCW wearing the respirator should inspect,
put on, fit check, and correctly wear the provided respirator (i.e., achieve
and maintain proper face-seal fit on the HCW's face).
* An opportunity to handle the provided respirator and learn how to
put it on, wear it properly, and check the important parts.
* Instruction in how to recognize an inadequately functioning respirator.
5. Face-seal fit testing and fit checking. HCWs should undergo fit testing
to identify a respirator that adequately fits each individual HCW. The
HCW should receive fitting instructions that include demonstrations and
practice in how the respirator should be worn, how it should be adjusted,
and how to determine if it fits properly. The HCW should be taught to check
the facepiece fit before each use.
6. Respirator inspection, cleaning, maintenance, and storage. Conscientious
respirator maintenance should be an integral part of an overall respirator
program. This maintenance applies both to respirators with replaceable
filters and respirators that are classified as disposable but that are
reused. Manufacturers' instructions for inspecting, cleaning, and maintaining
respirators should be followed to ensure that the respirator continues
to function properly (55).
7. Periodic evaluation of the personal respiratory protection program.
The program should be evaluated completely at least once a year, and both
the written operating procedures and program administration should be revised
as necessary based on the results of the evaluation. Elements of the program
that should be evaluated include work practices and employee acceptance
of respirator use (i.e., subjective comments made by employees concerning
comfort during use and interference with duties).
Supplement 5: Decontamination -- Cleaning, Disinfecting, and
Sterilizing of Patient-Care Equipment
Equipment used on patients who have TB is usually not involved in the
transmission of M. tuberculosis, although transmission by contaminated
bronchoscopes has been demonstrated (159,160). Guidelines for cleaning,
disinfecting, and sterilizing equipment have been published (161,162).
The rationale for cleaning, disinfecting, or sterilizing patient-care equipment
can be understood more readily if medical devices, equipment, and surgical
materials are divided into three general categories. These categories --
critical, semicritical, and noncritical items -- are defined by the potential
risk for infection associated with their use (163,164).
Critical items are instruments that are introduced directly into the
bloodstream or into other normally sterile areas of the body (e.g., needles,
surgical instruments, cardiac catheters, and implants). These items should
be sterile at the time of use.
Semicritical items are those that may come in contact with mucous membranes
but do not ordinarily penetrate body surfaces (e.g., noninvasive flexible
and rigid fiberoptic endoscopes or bronchoscopes, endotracheal tubes, and
anesthesia breathing circuits). Although sterilization is preferred for
these instruments, high-level disinfection that destroys vegetative microorganisms,
most fungal spores, tubercle bacilli, and small nonlipid viruses may be
used. Meticulous physical cleaning of such items before sterilization or
high-level disinfection is essential.
Noncritical items are those that either do not ordinarily touch the
patient or touch only the patient's intact skin (e.g., crutches, bedboards,
blood pressure cuffs, and various other medical accessories). These items
are not associated with direct transmission of M. tuberculosis, and washing
them with detergent is usually sufficient.
Health-care facility policies should specify whether cleaning, disinfecting,
or sterilizing an item is necessary to decrease the risk for infection.
Decisions about decontamination processes should be based on the intended
use of the item, not on the diagnosis of the patient for whom the item
was used. Selection of chemical disinfectants depends on the intended use,
the level of disinfection required, and the structure and material of the
item to be disinfected.
Although microorganisms are ordinarily found on walls, floors, and other
environmental surfaces, these surfaces are rarely associated with transmission
of infections to patients or HCWs. This is particularly true with organisms
such as M. tuberculosis, which generally require inhalation by the host
for infection to occur. Therefore, extraordinary attempts to disinfect
or sterilize environmental surfaces are not indicated. If a detergent germicide
is used for routine cleaning, a hospital-grade, EPA-approved germicide/disinfectant
that is not tuberculocidal can be used. The same routine daily cleaning
procedures used in other rooms in the facility should be used to clean
TB isolation rooms, and personnel should follow isolation practices while
cleaning these rooms. For final cleaning of the isolation room after a
patient has been discharged, personal protective equipment is not necessary
if the room has been ventilated for the appropriate amount of time (Table
S3-1).
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Glossary
This glossary contains many of the terms used in the guidelines, as
well as others that are encountered frequently by persons who implement
TB infection-control programs. The definitions given are not dictionary
definitions but are those most applicable to usage relating to TB.
Acid-fast bacilli (AFB): Bacteria that retain certain dyes after
being washed in an acid solution. Most acid-fast organisms are mycobacteria.
When AFB are seen on a stained smear of sputum or other clinical specimen,
a diagnosis of TB should be suspected; however, the diagnosis of TB is
not confirmed until a culture is grown and identified as M. tuberculosis.
Adherence: Refers to the behavior of patients when they follow
all aspects of the treatment regimen as prescribed by the medical provider,
and also refers to the behavior of HCWs and employers when they follow
all guidelines pertaining to infection control.
Aerosol: The droplet nuclei that are expelled by an infectious
person (e.g., by coughing or sneezing); these droplet nuclei can remain
suspended in the air and can transmit M. tuberculosis to other persons.
AIA: The American Institute of Architects, a professional body
that develops standards for building ventilation.
Air changes: The ratio of the volume of air flowing through a
space in a certain period of time (i.e., the airflow rate) to the volume
of that space (i.e., the room volume); this ratio is usually expressed
as the number of air changes per hour (ACH).
Air mixing: The degree to which air supplied to a room mixes
with the air already in the room, usually expressed as a mixing factor.
This factor varies from 1 (for perfect mixing) to 10 (for poor mixing),
and it is used as a multiplier to determine the actual airflow required
(i.e., the recommended ACH multiplied by the mixing factor equals the actual
ACH required).
Alveoli: The small air sacs in the lungs that lie at the end
of the bronchial tree; the site where carbon dioxide in the blood is replaced
by oxygen from the lungs and where TB infection usually begins.
Anergy: The inability of a person to react to skin-test antigens
(even if the person is infected with the organisms tested) because of immunosuppression.
Anteroom: A small room leading from a corridor into an isolation
room; this room can act as an airlock, preventing the escape of contaminants
from the isolation room into the corridor.
Area: A structural unit (e.g., a hospital ward or laboratory)
or functional unit (e.g., an internal medicine service) in which HCWs provide
services to and share air with a specific patient population or work with
clinical specimens that may contain viable M. tuberculosis organisms. The
risk for exposure to M. tuberculosis in a given area depends on the prevalence
of TB in the population served and the characteristics of the environment.
ASHRAE: The American Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc., a professional body that develops standards for building
ventilation.
Asymptomatic: Without symptoms, or producing no symptoms.
Bacillus of Calmette and Guerin (BCG) vaccine: A TB vaccine used
in many parts of the world.
BACTEC(R): One of the most often used radiometric methods for
detecting the early growth of mycobacteria in culture. It provides rapid
growth (in 7-14 days) and rapid drug-susceptibility testing (in 5-6 days).
When BACTEC(R) is used with rapid species identification methods, M. tuberculosis
can be identified within 10-14 days of specimen collection.
Booster phenomenon: A phenomenon in which some persons (especially
older adults) who are skin tested many years after infection with M. tuberculosis
have a negative reaction to an initial skin test, followed by a positive
reaction to a subsequent skin test. The second (i.e., positive) reaction
is caused by a boosted immune response. Two-step testing is used to distinguish
new infections from boosted reactions (see Two-step testing).
Bronchoscopy: A procedure for examining the respiratory tract
that requires inserting an instrument (a bronchoscope) through the mouth
or nose and into the trachea. The procedure can be used to obtain diagnostic
specimens.
Capreomycin: An injectable, second-line anti-TB drug used primarily
for the treatment of drug-resistant TB.
Cavity: A hole in the lung resulting from the destruction of
pulmonary tissue by TB or other pulmonary infections or conditions. TB
patients who have cavities in their lungs are referred to as having cavitary
disease, and they are often more infectious than TB patients without cavitary
disease.
Chemotherapy: Treatment of an infection or disease by means of
oral or injectable drugs.
Cluster: Two or more PPD skin-test conversions occurring within
a 3-month period among HCWs in a specific area or occupational group, and
epidemiologic evidence suggests occupational (nosocomial) transmission.
Contact: A person who has shared the same air with a person who
has infectious TB for a sufficient amount of time to allow possible transmission
of M. tubercuosis.
Conversion, PPD: See PPD test conversion.
Culture: The process of growing bacteria in the laboratory so
that organisms can be identified.
Cycloserine: A second-line, oral anti-TB drug used primarily
for treating drug-resistant TB.
Directly observed therapy (DOT): An adherence-enhancing strategy
in which an HCW or other designated person watches the patient swallow
each dose of medication.
DNA probe: A technique that allows rapid and precise identification
of mycobacteria (e.g., M. tuberculosis and M. bovis) that are grown in
culture. The identification can often be completed in 2 hours.
Droplet nuclei: Microscopic particles (i.e., 1-5 um in diameter)
produced when a person coughs, sneezes, shouts, or sings. The droplets
produced by an infectious TB patient can carry tubercle bacilli and can
remain suspended in the air for prolonged periods of time and be carried
on normal air currents in the room.
Drug resistance, acquired: A resistance to one or more anti-TB
drugs that develops while a patient is receiving therapy and which usually
results from the patient's nonadherence to therapy or the prescription
of an inadequate regimen by a health-care provider.
Drug resistance, primary: A resistance to one or more anti-TB
drugs that exists before a patient is treated with the drug(s). Primary
resistance occurs in persons exposed to and infected with a drug-resistant
strain of M. tuberculosis.
Drug-susceptibility pattern: The anti-TB drugs to which the tubercle
bacilli cultured from a TB patient are susceptible or resistant based on
drug-susceptibility tests.
Drug-susceptibility tests: Laboratory tests that determine whether
the tubercle bacilli cultured from a patient are susceptible or resistant
to various anti-TB drugs.
Ethambutol: A first-line, oral anti-TB drug sometimes used concomitantly
with INH, rifampin, and pyrazinamide.
Ethionamide: A second-line, oral anti-TB drug used primarily
for treating drug-resistant TB.
Exposure: The condition of being subjected to something (e.g.,
infectious agents) that could have a harmful effect. A person exposed to
M. tuberculosis does not necessarily become infected (see Transmission).
First-line drugs: The most often used anti-TB drugs (i.e., INH,
rifampin, pyrazinamide, ethambutol, and streptomycin).
Fixed room-air HEPA recirculation systems: Nonmobile devices
or systems that remove airborne contaminants by recirculating air through
a HEPA filter. These may be built into the room and permanently ducted
or may be mounted to the wall or ceiling within the room. In either situation,
they are fixed in place and are not easily movable.
Fluorochrome stain: A technique for staining a clinical specimen
with fluorescent dyes to perform a microscopic examination (smear) for
mycobacteria. This technique is preferable to other staining techniques
because the mycobacteria can be seen easily and the slides can be read
quickly.
Fomites: Linens, books, dishes, or other objects used or touched
by a patient. These objects are not involved in the transmission of M.
tuberculosis.
Gastric aspirate: A procedure sometimes used to obtain a specimen
for culture when a patient cannot cough up adequate sputum. A tube is inserted
through the mouth or nose and into the stomach to recover sputum that was
coughed into the throat and then swallowed. This procedure is particularly
useful for diagnosis in children, who are often unable to cough up sputum.
High-efficiency particulate air (HEPA) filter: A specialized
filter that is capable of removing 99.97% of particles greater than or
equal to 0.3 um in diameter and that may assist in controlling the transmission
of M. tuberculosis. Filters may be used in ventilation systems to remove
particles from the air or in personal respirators to filter air before
it is inhaled by the person wearing the respirator. The use of HEPA filters
in ventilation systems requires expertise in installation and maintenance.
Human immunodeficiency virus (HIV) infection: Infection with
the virus that causes acquired immunodeficiency syndrome (AIDS). HIV infection
is the most important risk factor for the progression of latent TB infection
to active TB.
Immunosuppressed: A condition in which the immune system is not
functioning normally (e.g., severe cellular immunosuppression resulting
from HIV infection or immunosuppressive therapy). Immunosuppressed persons
are at greatly increased risk for developing active TB after they have
been infected with M. tuberculosis. No data are available regarding whether
these persons are also at increased risk for infection with M. tuberculosis
after they have been exposed to the organism.
Induration: An area of swelling produced by an immune response
to an antigen. In tuberculin skin testing or anergy testing, the diameter
of the indurated area is measured 48-72 hours after the injection, and
the result is recorded in millimeters.
Infection: The condition in which organisms capable of causing
disease (e.g., M. tuberculosis) enter the body and elicit a response from
the host' s immune defenses. TB infection may or may not lead to clinical
disease.
Infectious: Capable of transmitting infection. When persons who
have clinically active pulmonary or laryngeal TB disease cough or sneeze,
they can expel droplets containing M. tuberculosis into the air. Persons
whose sputum smears are positive for AFB are probably infectious.
Injectable: A medication that is usually administered by injection
into the muscle (intramuscular [IM]) or the bloodstream (intravenous [IV]).
Intermittent therapy: Therapy administered either two or three
times per week, rather than daily. Intermittent therapy should be administered
only under the direct supervision of an HCW or other designated person
(see Directly observed therapy [DOT]).
Intradermal: Within the layers of the skin.
Isoniazid (INH): A first-line, oral drug used either alone as
preventive therapy or in combination with several other drugs to treat
TB disease.
Kanamycin: An injectable, second-line anti-TB drug used primarily
for treatment of drug-resistant TB.
Latent TB infection: Infection with M. tuberculosis, usually
detected by a positive PPD skin-test result, in a person who has no symptoms
of active TB and who is not infectious.
Mantoux test: A method of skin testing that is performed by injecting
0.1 mL of PPD-tuberculin containing 5 tuberculin units into the dermis
(i.e., the second layer of skin) of the forearm with a needle and syringe.
This test is the most reliable and standardized technique for tuberculin
testing (see Tuberculin skin test and Purified protein derivative [PPD]-tuberculin
test).
Multidrug-resistant tuberculosis (MDR-TB): Active TB caused by
M. tuberculosis organisms that are resistant to more than one anti-TB drug;
in practice, often refers to organisms that are resistant to both INH and
rifampin with or without resistance to other drugs (see Drug resistance,
acquired and Drug resistance, primary).
M. tuberculosis complex: A group of closely related mycobacterial
species that can cause active TB (e.g., M. tuberculosis, M. bovis, and
M. africanum); most TB in the United States is caused by M. tuberculosis.
Negative pressure: The relative air pressure difference between
two areas in a health-care facility. A room that is at negative pressure
has a lower pressure than adjacent areas, which keeps air from flowing
out of the room and into adjacent rooms or areas.
Nosocomial: An occurrence, usually an infection, that is acquired
in a hospital or as a result of medical care.
Para-aminosalicylic acid: A second-line, oral anti-TB drug used
for treating drug-resistant TB.
Pathogenesis: The pathologic, physiologic, or biochemical process
by which a disease develops.
Pathogenicity: The quality of producing or the ability to produce
pathologic changes or disease. Some nontuberculous mycobacteria are pathogenic
(e.g., Mycobacterium kansasii), and others are not (e.g., Mycobacterium
phlei).
Portable room-air HEPA recirculation units: Free-standing portable
devices that remove airborne contaminants by recirculating air through
a HEPA filter.
Positive PPD reaction: A reaction to the purified protein derivative
(PPD)-tuberculin skin test that suggests the person tested is infected
with M. tuberculosis. The person interpreting the skin-test reaction determines
whether it is positive on the basis of the size of the induration and the
medical history and risk factors of the person being tested.
Preventive therapy: Treatment of latent TB infection used to
prevent the progression of latent infection to clinically active disease.
Purified protein derivative (PPD)-tuberculin: A purified tuberculin
preparation that was developed in the 1930s and that was derived from old
tuberculin. The standard Mantoux test uses 0.1 mL of PPD standardized to
5 tuberculin units.
Purified protein derivative (PPD)-tuberculin test: A method used
to evaluate the likelihood that a person is infected with M. tuberculosis.
A small dose of tuberculin (PPD) is injected just beneath the surface of
the skin, and the area is examined 48-72 hours after the injection. A reaction
is measured according to the size of the induration. The classification
of a reaction as positive or negative depends on the patient's medical
history and various risk factors (see Mantoux test).
Purified protein derivative (PPD)-tuberculin test conversion:
A change in PPD test results from negative to positive. A conversion within
a 2-year period is usually interpreted as new M. tuberculosis infection,
which carries an increased risk for progression to active disease. A booster
reaction may be misinterpreted as a new infection (see Booster phenomenon
and Two-step testing).
Pyrazinamide: A first-line, oral anti-TB drug used in treatment
regimens.
Radiography: A method of viewing the respiratory system by using
radiation to transmit an image of the respiratory system to film. A chest
radiograph is taken to view the respiratory system of a person who is being
evaluated for pulmonary TB. Abnormalities (e.g., lesions or cavities in
the lungs and enlarged lymph nodes) may indicate the presence of TB.
Radiometric method: A method for culturing a specimen that allows
for rapid detection of bacterial growth by measuring production of CO(2)
by viable organisms; also a method of rapidly performing susceptibility
testing of M. tuberculosis.
Recirculation: Ventilation in which all or most of the air that
is exhausted from an area is returned to the same area or other areas of
the facility.
Regimen: Any particular TB treatment plan that specifies which
drugs are used, in what doses, according to what schedule, and for how
long.
Registry: A record-keeping method for collecting clinical, laboratory,
and radiographic data concerning TB patients so that the data can be organized
and made available for epidemiologic study.
Resistance: The ability of some strains of bacteria, including
M. tuberculosis, to grow and multiply in the presence of certain drugs
that ordinarily kill them; such strains are referred to as drug-resistant
strains.
Rifampin: A first-line, oral anti-TB drug that, when used concomitantly
with INH and pyrazinamide, provides the basis for short-course therapy.
Room-air HEPA recirculation systems and units: Devices (either
fixed or portable) that remove airborne contaminants by recirculating air
through a HEPA filter.
Second-line drugs: Anti-TB drugs used when the first-line drugs
cannot be used (e.g., for drug-resistant TB or because of adverse reactions
to the first-line drugs). Examples are cycloserine, ethionamide, and capreomycin.
Single-pass ventilation: Ventilation in which 100% of the air
supplied to an area is exhausted to the outside.
Smear (AFB smear): A laboratory technique for visualizing mycobacteria.
The specimen is smeared onto a slide and stained, then examined using a
microscope. Smear results should be available within 24 hours. In TB, a
large number of myco-bacteria seen on an AFB smear usually indicates infectiousness.
However, a positive result is not diagnostic of TB because organisms other
than M. tuberculosis may be seen on an AFB smear (e.g., nontuberculous
mycobacteria).
Source case: A case of TB in an infectious person who has transmitted
M. tuberculosis to another person or persons.
Source control: Controlling a contaminant at the source of its
generation, which prevents the spread of the contaminant to the general
work space.
Specimen: Any body fluid, secretion, or tissue sent to a laboratory
where smears and cultures for M. tuberculosis will be performed (e.g.,
sputum, urine, spinal fluid, and material obtained at biopsy).
Sputum: Phlegm coughed up from deep within the lungs. If a patient
has pulmonary disease, an examination of the sputum by smear and culture
can be helpful in evaluating the organism responsible for the infection.
Sputum should not be confused with saliva or nasal secretions.
Sputum induction: A method used to obtain sputum from a patient
who is unable to cough up a specimen spontaneously. The patient inhales
a saline mist, which stimulates a cough from deep within the lungs.
Sputum smear, positive: AFB are visible on the sputum smear when
viewed under a microscope. Persons with a sputum smear positive for AFB
are considered more infectious than those with smear-negative sputum.
Streptomycin: A first-line, injectable anti-TB drug.
Symptomatic: Having symptoms that may indicate the presence of
TB or another disease (see Asymptomatic).
TB case: A particular episode of clinically active TB. This term
should be used only to refer to the disease itself, not the patient with
the disease. By law, cases of TB must be reported to the local health department.
TB infection: A condition in which living tubercle bacilli are
present in the body but the disease is not clinically active. Infected
persons usually have positive tuberculin reactions, but they have no symptoms
related to the infection and are not infectious. However, infected persons
remain at lifelong risk for developing disease unless preventive therapy
is given.
Transmission: The spread of an infectious agent from one person
to another. The likelihood of transmission is directly related to the duration
and intensity of exposure to M. tuberculosis (see Exposure).
Treatment failures: TB disease in patients who do not respond
to chemotherapy and in patients whose disease worsens after having improved
initially.
Tubercle bacilli: M. tuberculosis organisms.
Tuberculin skin test: A method used to evaluate the likelihood
that a person is infected with M. tuberculosis. A small dose of PPD-tuberculin
is injected just beneath the surface of the skin, and the area is examined
48-72 hours after the injection. A reaction is measured according to the
size of the induration. The classification of a reaction as positive or
negative depends on the patient's medical history and various risk factors
(see Mantoux test, PPD test).
Tuberculosis (TB): A clinically active, symptomatic disease caused
by an organism in the M. tuberculosis complex (usually M. tuberculosis
or, rarely, M. bovis or M. africanum).
Two-step testing: A procedure used for the baseline testing of
persons who will periodically receive tuberculin skin tests (e.g., HCWs)
to reduce the likelihood of mistaking a boosted reaction for a new infection.
If the initial tuberculin-test result is classified as negative, a second
test is repeated 1-3 weeks later. If the reaction to the second test is
positive, it probably represents a boosted reaction. If the second test
result is also negative, the person is classified as not infected. A positive
reaction to a subsequent test would indicate new infection (i.e., a skin-test
conversion) in such a person.
Ultraviolet germicidal irradiation (UVGI): The use of ultraviolet
radiation to kill or inactivate microorganisms.
Ultraviolet germicidal irradiation (UVGI) lamps: Lamps that kill
or inactivate microorganisms by emitting ultraviolet germicidal radiation,
predominantly at a wavelength of 254 nm (intermediate light waves between
visible light and X-rays). UVGI lamps can be used in ceiling or wall fixtures
or within air ducts of ventilation systems.
Ventilation, dilution: An engineering control technique to dilute
and remove airborne contaminants by the flow of air into and out of an
area. Air that contains droplet nuclei is removed and replaced by contaminant-free
air. If the flow is sufficient, droplet nuclei become dispersed, and their
concentration in the air is diminished.
Ventilation, local exhaust: Ventilation used to capture and remove
airborne contaminants by enclosing the contaminant source (i.e., the patient)
or by placing an exhaust hood close to the contaminant source.
Virulence: The degree of pathogenicity of a microorganism as
indicated by the severity of the disease produced and its ability to invade
the tissues of a host. M. tuberculosis is a virulent organism.
INDEX
Acid-fact bacilli smears (see Smears, AFB) Acquired immunodeficiency
syndrome (see HIV infection) Administrative controls ...........................................
2, 3, 33 Aerosol therapy .......................................... 5,
33, 34, 69, 70 Aerosolized pentamidine Booths for administration ........................................
70, 71 Patient screening ....................................................
35 Risk for nosocomial transmission of M. tuberculosis ...................
5 Tents for administration ......................................... 70,
71 AFB smears (see Smears, AFB) AIDS (see HIV infection) Air changes per
hour (ACH) .............................. 21, 29, 30, 84, 87 ASHRAE recommendations
....................................... 29, 51, 69 Determining ..............................................
29, 72, 74, 75 Removal efficiencies .............................................
70, 72 Airflow Monitoring direction ..........................................
69, 78-81 Ambulatory-care settings/areas Management of patients ....................................
13, 20, 25-27 American Conference of Governmental Industrial Hygienists,
Inc. (ACGIH) ............................................. 69 American
Institute of Architects (AIA) .......................... 29, 69, 87 American
Society of Hearing, Refrigerating and Air-Conditioning Engineers, Inc.
(ASHRAE) ................ 29, 51, 69, 87 Americans With Disabilities Act
of 1990 ................................. 38 Anergy testing ..................................................
37, 38, 62 Anesthesia considerations ...........................................
35, 50 Anterooms........................................................
30, 50, 77 Negative pressure for ................................................
77 Assignment of responsibility ................................ 8, 12,
20, 102 Autopsy Risk for nosocomial transmission of M. Tuberculosis ...........
5, 33, 99 Autopsy rooms ................................................
5, 33, 51, 99 HEPA filtration ......................................................
51 Respiratory protection ........................................... 51,
99 UVGI .................................................................
51 Bacteriology Collecting specimens .............................................
24, 64 Mixed mycobacterial infection ........................................
64 BCG (Bacille of Calmette and Guerin) vaccine ..................... 5,
39, 90 Skin testing .....................................................
39, 63 Vaccination ...................................................
5, 39, 63 Bronchoscopy ....................................................
34, 35, 64 Ventilation ..........................................................
35 Chest radiography (see Diagnosis of TB) Cluster (see PPD testing) ...................................
10, 11, 16, 17 Cohorting ...............................................................
27 Community TB profile ............................................. 9,
12, 17 Confidentiality .................................. 3, 18, 36, 38,
40, 48, 49 Contact investigation ................................ 36, 42,
43, 47-50, 63 Correctional facilities .................................................
52 Cough-inducing procedures .................................... 6, 14,
21, 58 Bronchoscopy .........................................................
35 General guidelines ....................................... 19, 21, 34,
35 Home-health-care settings ............................................
54 In ambulatory-care areas .............................................
26 Patient recovery from ................................................
35 Pentamidine, aerosolized ..........................................
6, 35 Respiratory protection ........................................ 33-35,
97 Risk for nosocomial transmission of M. tuberculosis ...............
7, 27 Sputum induction ......................................................
6 Counseling ......................................... 6, 7, 14, 21, 37,
53-55 Immunocompromised workers ............................... 6, 7, 21,
53-55 Culture methods Radiometric ......................................................
24, 64 Decontamination of patient-care equipment ..............................
105 Supplement 5--Decontamination, disinfecting, and sterilizing of patient-care
equipment ............................ 105 Dental care .....................................................
33, 52, 53 Dental settings Infection-control precautions, TB ................................
52, 53 PPD screening program ........................................ 16,
48, 50 Risk assessment ...............................................
8, 16, 52 Diagnosis TB ........................................ 12, 13,
24, 26, 27, 51 Anergy testing ...........................................
37, 38, 59, 62 Bacteriology (see Smears, AFB and Culture methods) Before
aerosol therapy ............................................... 35 Bronchoscopy
..................................................... 35, 64 Chest radiograph
......................................... 25, 28, 49, 50 Culturing ........................................................
49, 50 DNA probes ............................................... 11, 18,
27, 48 Fluorescent microscopy ...............................................
24 High-pressure liquid chromatography ..................................
24 Hospitalized patients ............................................ 27,
28 Index of suspicion ............................................ 8, 24,
59 Mantoux technique ....................................................
59 Medical history .................................................. 12,
53 NAP test .............................................................
24 Nucleic acid probes .............................................. 24,
64 PPD testing ..........................................................
25 Radiometric culture .............................................. 24,
25 Smears ....................................................... 24, 25,
64 Supplement 2 -- Diagnosis and treatment of latent TB infection and active
TB ........................................... 59 With anergy ..........................................................
25 With immunocompromising conditions ...................................
25 With simultaneous pulmonary infection ................................
25 Directly observed therapy (DOT) ................................. 25,
53, 66 Home-health-care settings ........................................
53, 66 Public health department .........................................
25, 66 Discharge planning ........................................... 9,
13, 31, 49 Drug-resistant TB ..................... 2, 6, 11, 19, 27, 30,
37, 48, 57, 66 Drug-susceptibility testing ..................................
9, 24, 28, 66 On initial isolates ..............................................
28, 66 Radiometric methods ..................................................
24 Reporting to public health department ................................
66 Education and training ................... 2, 14, 19, 21, 36, 51, 53,
55, 92 Emergency medical services ................................... 3,
33, 51, 52 PPD screening program ................................................
52 Respiratory protection ........................................... 33,
51 Emergency departments ........................................ 3, 20,
25, 32 Management of patients ...........................................
13, 25 Endotracheal intubation ..................................... 5,
34, 52, 105 Engineering controls ................ 2, 3, 7, 12, 13, 20,
21, 29-33, 47, 69 Epidemiology, pathogenesis, and transmission of M. tuberculosis
.................................................... 4, 5 Executive summary
..................................................... 1, 2 General ventilation
.................................. 20, 26, 29-31, 73, 69 Dilution and removal
....................................... 5, 7, 30, 73 Facility airflow direction
.................................... 73, 76-81 Mixing factor ........................................................
75 Negative pressure ......................................... 29, 76-81,
86 Recirculating systems ..................... 20, 29, 30, 32, 73, 82-84,
88 Room airflow patterns .............................................
73-75 Short-circuiting .................................................
74, 75 Single-pass systems ..............................................
20, 73 Glossary ...............................................................
113 Health-care facility, definition .........................................
3 Health-care worker(s) (HCW[s]) Confidentiality ...................................
3, 18, 36, 38, 40, 48 Counseling ......................................
6, 8, 14, 21, 37, 53-55 Risk for infection ................................................
37 Risk for infection and disease in immunocompromised HCWs .....................................
37, 38 Job reassignment ..................................................
38 Definition ...............................................................
3 Education and training .................... 2, 14, 19, 21, 36, 51, 53-55,
92 Evaluating PPD conversions ..............................................
37 Evaluating positive PPD-test results ................................
14, 37 Immunocompromised ...................................................
36, 37 Preventive therapy ..............................................
36, 37, 65 Screening for active TB .............................................
14, 38 Screening for latent TB infection ...................................
14, 38 Training ................................................................
36 Workplace restrictions ..................................................
41 Active TB ........................................................ 38,
41 Latent TB infection ..................................................
41 Health department ................................. 8, 21, 25, 31, 43,
47-50 Case notification ............................................ 25,
43, 48 Health Resources and Services Administration ........................
29, 87 Heat wheel energy recovery units, HEPA filtration for...................................................
82 Hierarchy of controls ...................................... 1, 6, 7,
36, 86 High-effeciency particulate (HEPA filtration .........................
81-87 Autopsy rooms ........................................................
51 Disposable prefilters to extend life ............................. 85,
86 DOP penetration test .................................................
85 Efficiency ............................................... 32, 81, 85,
86 Enclosing booth use .................................. 32, 71, 73, 81,
82 In ambulatory-care areas ......................................... 26,
32 Individual room-air recirculation ......................... 32, 81-84,
86 Installation, maintenance, and monitoring .................... 32, 81,
85 Longevity ........................................................ 85,
86 Pressure-sensing device to determine replacement need ..............................................................
85 Recirculation of HEPA-filtered air within a room .. 20, 21, 30, 59,
81-84 Evaluation .................................................... 69,
84 Fixed room-air recirculation systems ............... 29, 32, 81-84,
86 Portable room-air recirculation units ......... 29, 32, 81, 82, 84,
86 Recirculation of HEPA-filtered air to other areas of facility ..............................................
30, 32, 81, 82 Use when exhausting air to the outside ............... 32,
73, 74, 81, 82 High-risk area ........................................
9, 10, 12-15, 17, 22 HIV infection Anergy testing Cell-mediated immunity,
impaired ............................. 25, 36, 37 Chest radiography ....................................................
25 Coinfection with M. tuberculosis ............................... 4,
5, 36 Counseling HIV-infected HCWs ......................................
36-38 Evaluation of PPD skin-test results .......................... 25,
38, 61 Likelihood of infection after exposure to M. tuberculosis ....................................................
5 Progression from latent TB infection to active TB ...................
4-6 Smears, AFB ..........................................................
25 Home-health-care settings ............................................
3, 53 Cough-inducing procedures ............................................
54 PPD screening program ................................................
54 Respiratory protection ........................................... 53,
54 Hospices .............................................................
3, 52 Human immunodeficiency virus (see HIV infection) Infection control
Development of the TB infection-control plan ..........................
8 Engineering controls .........3, 7, 12, 20, 21, 31, 33, 47, 53, 55, 69-95
Evaluation of engineering controls ...................................
19 Fundamentals ................................................. 6-8,
12-15 Hierarchy of control measures .........................................
6 Observation of infection-control practices ....................... 12,
19 Infection-control practices, evaluating effectiveness ...................
19 Infectiousness Determining ......................................................
57, 58 Factors determining ...................................... 27, 40,
41, 57 In HIV-infected patients .............................................
57 Length of, on therapy ................................................
57 Monitoring ...........................................................
58 Pediatric patients ............................................... 27,
57 Supplement 1--Determining the infectiousness of a TB patient .....................................................57,
58 Noninfectiousness ....................................................
31 Intensive-care units ....................................................
27 Intermediate-risk area ....................................... 9, 16,
17, 22 Isolation practices Dental settings ..................................................
52, 53 Discontinuation .......................................... 13, 27,
30, 31 Facilitating patient adherence .......................................
28 For multidrug-resistant TB ...........................................
31 Initiation ....................................................... 13,
27 Intensive-care units .................................................
27 Keeping door to room closed .................................. 28, 29,
79 Long-term-care facilities ............................................
52 Minimizing access to room ............................................
28 Patient education ....................................................
28 Pediatric patients ...................................................
27 Visitors ......................................................... 27,
28 Isolation rooms Air changes per hour (ACH) ...............................
29, 72, 74, 87 Air exhaust ......................................................
29, 87 Anteroom .............................................................
30 Grouping .............................................................
30 HEPA filtration .................................................. 30,
86 Keeping door to room closed ...................................... 29,
77 Negative pressure ................................................ 29,
87 Number required .................................................. 13,
30 Purpose .......................................................... 29,
86 Ultraviolet germicidal irradiation (UVGI) ........................ 30,
86 Isoniazid (INH) During pregnancy .....................................................
65 Hepatitis ............................................................
65 Monitoring for adverse reactions .....................................
66 Preventive therapy regimen ...........................................
65 Laboratories ......................................... 3, 12, 23, 24,
51, 59 Local exhaust ventilation ............................. 7, 20, 21,
35, 69-73 Discharge from booths, tents, and hoods ......................
70, 71, 73 Exterior devices .................................................
70, 71 Into TB isolation rooms ..........................................
71, 73 Long-term-care facilities ...............................................
52 Low-risk areas ........................................... 9, 10, 16,
22, 23 Medical offices ..................................................
3, 54, 55 Medical record review .................................... 9,
18, 19, 24, 49 Minimal-risk facility .............................................
9-11, 23 Mycobacterium avium complex .........................................
25, 64 National Institute for Occupational Safety and Health (NIOSH) ...................................
34, 91-93, 98, 99, 102 Negative pressure Alternate methods for achieving
.................................. 77, 78 Definition ...........................................................
76 Monitoring .................................................... 29,
78-80 Pressure differential required ....................................76,
77 Pressure-sensing devices............................................79-81
Pressurizing the corridor ............................................
78 Smoke-tube testing ................................... 74, 75, 78, 79,
81 TB isolation rooms ........................................... 29, 80,
81 Tents and booths ................................................. 71,
73 Nosocomial transmission ............................ 3, 5, 11, 16-18,
21, 47 Factors promoting ..............................................
5, 6, 23 Occupational groups ..........................................
10, 11, 16-19 Occupational Safety and Health Administration (OSHA) ...33,
34, 98, 100, 102 Operating rooms .........................................................
50 Anterooms ............................................................
50 Respiratory protection ........................................... 50,
51 Ventilation ...................................................... 35,
50 OSHA respiratory protection standard ...................... 34, 98,
100, 102 Outbreaks of TB in health-care facilities .....................
2, 6, 50, 97 Patient-to-patient transmission Cohorting ............................................................
27 Investigating ........................................................
48 Pediatric patients .............................................. 27,
57, 68 Pneumocystis carinii ................................................
25, 36 PPD reading Cut-points for risk groups ....................................
60-63, 65 PPD testing .............................................................
53 Analysis of increased conversion rate ........................ 11, 12,
18 Anergy ................................................... 37, 38, 54,
61 BCG vaccination .......................................... 37, 39, 54,
63 Booster phenomenon ............................................... 55,
63 Cluster ...................................................... 10, 11,
17 Contact investigation ...................... 8, 25, 36, 42, 43, 47-50,
61 Conversions ............... 8, 11, 16-23, 36, 37, 39-45, 47-49, 60-63,
65 Dental settings ......................................................
53 Emergency medical services ....................................... 51,
52 Evaluating PPD conversion ..................... 8, 18, 20, 21, 36, 39,
47 Frequency ................................. 18, 21, 38-40, 43, 49, 52,
54 HCWs with positive PPD test ............................... 12, 14,
39-41 Home-health-care settings .................................... 14,
53, 54 Immunocompromised workers ....................... 4-6, 21, 26, 31,
37, 38 Interpretation of results .........................................
60-64 Mantoux technique ....................................................
59 Occupational group ....................................... 10, 11, 17,
40 Persons with HIV infection ........................ 25, 38, 39, 60-62,
65 Positive-predictive value .................................... 60, 61,
63 Pregnancy ............................................................
61 Recent PPD converters ..................................... 40, 60-63,
65 Recording results ............................................ 17, 18,
40 Self-reading results .................................................
59 Staggered testing ....................................................
39 Two-step testing ................................................. 39,
63 Preventive therapy ..................................................
65, 66 Drug-susceptibility testing ......................................
40, 42 For anergic persons ..................................................
65 Monitoring ...........................................................
66 Pregnancy ............................................................
65 Regimens .............................................................
65 Problem evaluation ............................................... 14,
41-49 Active TB in HCWs ..................................... 14, 40-42,
47, 48 Contact investigation .........................................
43, 48-50 Patient-to-patient transmission ..............................
14, 48, 49 PPD test conversions in HCWs ..................................
42-45, 47 Public health department Contact investigation ....................................
15, 25, 49, 50 Coordination .............................................
21, 25, 49, 50 Directly observed therapy (DOT) ..............................
25, 31, 66 Discharge planning ....................................... 13,
25, 31, 66 Providing assistance ..................................... 31,
43, 47, 50 Reporting ................................................ 15,
25, 48, 50 Radiographs ............... 4, 5, 24, 35, 40, 42, 49, 57, 59-60,
62, 64, 103 Radiology department ............................................
28, 32, 49 Re-entrainment ......................................................
87, 88 Recommendations Aerosolized pentamidine ..........................................
35, 70 AFB smears ........................................... 24, 30, 41,
58, 64 Analysis of PPD screening data ...................................
11, 17 Anergy testing .......................................................
62 Anterooms .................................................... 30, 50,
77 Autopsy rooms ........................................................
51 Bronchoscopy ....................................... 35, 64, 76, 99,
105 Case surveillance ....................................................
17 Community TB profile ...................................... 9. 11, 12,
17 Contact investigation ..................................... 15, 43,
47-50 Correctional facilities ...........................................
3, 52 Cough-inducing procedures ........7, 11, 14, 19, 21, 27, 33-35, 52,
54-58 ........................................................... 76, 82,
97 Development of the TB infection-control plan .............. 6, 19, 51,
69 Diagnosis ..................... 30, 35, 37, 38, 40, 41, 49, 53, 55,
59-65 Discharge planning .................................... 8, 13, 25,
31, 66 Drug-susceptibility testing ............... 24, 25, 27 40, 42, 50,
58, 66 Emergency departments .............................. 3, 9, 20, 25,
31, 32 Emergency medical services ....................................
3, 51, 52 Engineering controls .................................... 7,
31-33, 69-95 Environmental/engineering evaluation ......................
9, 19, 20, 69 HCW counseling .............................. 6, 8, 14, 16,
21, 37, 53-55 HCW screening ........... 6, 8, 14, 17, 21, 37-39, 42, 43,
47, 51-54, 103 HEPA filtration .............. 30, 32, 69, 71, 73, 75, 81-87,
91, 98, 100 Home-health-care settings .....................................
3, 53, 54 Hospices ..........................................................
3, 52 Identification of patients who may have active TB ................
23, 24 Immunocompromised persons ......................... 6, 21, 26, 31,
37, 38 Infectiousness ................................... 27, 41, 53, 54,
57, 58 Initiation of TB isolation .......................... 5-7, 9, 13,
20, 27 Initiation of treatment .................... 5, 6, 17, 20, 23, 25,
40, 66 Isolation practices ...................................... 13, 27-29,
105 Correctional facilities ...........................................
52 Dental settings ............................................... 52,
53 Discontinuation of .................................... 27, 30, 53,
58 Laboratories ............................................. 13, 19, 24,
51 Long-term-care facilities ............................................
52 Managing hospitalized patients ................................... 13,
20 Managing patients In ambulatory-care settings .......................
13, 20, 25, 26, 55 In correctional facilities ....................................
20, 52 In dental settings ............................................
20, 52 In emergency departments .............................. 13, 20,
25, 26 In emergency medical services settings .................... 13,
20, 51 In home-health-care settings ..................................
20, 53 In hospices ...................................................
20, 53 In medical offices ........................................ 20,
54, 55 Mantoux technique ....................................................
59 Medical offices .................................................. 54,
55 Multidrug-resistant tuberculosis (MRD-TB) ............ 25, 26, 31, 37,
65 Observation of infection-control practices ................... 12, 19,
20 Operating rooms .................................................. 35,
50 Patient transport ........................................ 28, 33, 51,
97 Periodic reassessment .................................... 11, 12, 19,
20 Preventive therapy for TB infection ....................... 36-41, 65,
66 Problem evaluation ........................................ 14, 40-49,
51 Radiology department ..................................... 13, 15, 28,
49 Radiometric culture .............................................. 24,
25 Review of TB patient medical records ........... 9, 12, 17-20, 43, 47,
49 Risk assessment .. 7, 8-12, 16-20, 22, 23, 30, 38, 39, 51, 52, 54, 92,
99 Training ................. 6, 8, 21, 36, 37, 51, 54, 55, 59, 92, 102,
103 Treatment for active TB .9, 12, 17, 20, 23, 24, 30, 31, 35, 41, 59,
66-68 Treatment for latent TB ................................. 41, 65,
66, 103 Triage ................................................ 7, 11,
13, 16, 25 UVGI ............................... 7, 26, 30, 32, 33, 51,
69, 84, 88-92 UVGI maintenance ..................................................
92-95 Ventilation ................... 5-7, 20, 21, 26, 28-32, 35, 51, 54,
69-90 Waiting areas .......................... 5, 20, 26-28, 31, 32, 35,
53, 89 Work place restrictions ..............................................
41 Respiratory protection ........... 3, 6, 7, 13, 21, 28, 33-35, 50-55,
97-103 Cleaning .......................................................
104, 105 Cough-inducing procedures ................. 14, 19, 21, 33-35,
54, 55, 97 Dental settings ..................................................
52, 53 Effectiveness ....................................................
97-102 Emergency medical services ...........................................
51 Face-seal leakage ............................................ 33, 97-101
Filter leakage ......................................... 33, 97, 100, 101
Fit checking ......................................... 100, 101, 103, 104
Fit testing ....................................... 33, 98, 100, 101, 104
Home-health-care settings ........................................ 53,
54 Maintenance ....................................... 34, 99, 101, 103,
104 Medical screening ...................................................
103 Negative-pressure respirators .......................... 33, 99, 100,
103 NIOSH ............................................ 34, 91-93, 98, 99,
102 Operating rooms ..................................................
35, 50 OSHA respiratory protection standard ............... 33, 34, 98,
100, 102 Performance criteria .................................. 21, 33,
51, 97-99 Positive-pressure respirators ............................ 34,
50, 98-100 Respiratory protection programs ............. 7, 13, 21, 34,
100, 102-104 Reuse of respirators ......................................
101, 102, 104 Storage ........................................................
103, 104 Supplement 4--Respiratory protection ............................
97- 104 Surgery ..................................................... 33,
34, 105 Surgical masks for patients ............................... 26-28,
34, 53 Training ................................ 8, 21, 36, 51, 54, 55,
102, 103 Visitors of TB patients ................................. 27,
28, 34, 102 Respiratory protection program ..................................
13, 97-104 Elements ........................................................
102-104 Periodic evaluation .................................................
104 Risk assessment .......................................................
7-22 Case surveillance ................................................
12, 17 Community TB profile ..........................................
9, 11, 17 Elements of a risk assessment .....................................
9, 11 Examples .........................................................
22, 23 How to perform ...................................................
10, 11 Levels of risk ............................................. 9,
11, 12-17 Periodic reassessment ........................................
12, 19, 22 Review of TB patient medical records .......................
9, 12, 17-20 Risk area definitions ........................................
11, 16, 17 Who should conduct .................................................
3, 9 Risk factors for disease progression ...................... 4, 5,
37, 38, 60 Risk groups .........................................................
60, 62 Signs and symptoms of active TB ......................... 20, 24,
36, 41, 49 Skin testing (see PPD testing) smears, AFB ...................
5, 9, 18, 24, 25, 27, 30, 41, 50, 57, 58, 64 Smoke-tube testing ..................................................
74, 75 Smoke tubes .................................................. 74,
75, 78-81 Source control ...............................................
7, 69, 70, 71 Sputum induction .........................................
5, 23, 35, 57, 70 Surgical masks For patient transport ........................................
28, 34, 51 For patients in ambulatory-care areas or emergency departments
................................. 26, 34, 53-55 Visitors of TB patients
.............................................. 27 TB infection-control
program ................ 3, 6-8, 11, 19, 20, 36, 50, 69 Assigning supervisory
responsibility ............................... 7, 8 Elements of a TB infection-control
program ..................... 8, 11-19 TB isolation room .............................
8, 13, 17, 29, 30, 50, 86-88 Achieving negative pressure ..................................
29, 76, 77 Anterooms ....................................................
30, 50, 77 Cohorting ............................................................
27 Exhaust .............................................. 21, 29, 82, 83,
86 Grouping ......................................................... 30,
69 HEPA filtration .......................................... 29, 81, 84,
86 In ambulatory-case areas .............................................
26 Negative pressure ..................................... 21, 29, 76-80,
87 Purpose ..............................................................
86 Ventilation .............. 21, 26, 27, 29, 31, 32, 69, 73, 76, 81, 86,
87 TB patient scheduling ...............................................
26, 28 Tissues .................................................................
35 For hospitalized patients ............................................
28 For patients in ambulatory-case areas or emergency departments ........................................
20, 26 Home-health-care settings ............................................
53 Transporting TB patients .................................... 28, 33,
51, 97 Treatment for TB Adherence ........................................................
30, 36 Directly observed therapy (DOT) ..................................
25, 66 Dosage recommendations for children and adults ....................
66-68 Drug susceptibility ..............................................
17, 67 For active TB ..................................... 17, 40, 42,
66, 67 For latent TB infection ................................... 40,
42, 66 During pregnancy .....................................................
65 For active TB ................................................. 66,
67 For latent TB infection ...........................................
65 Initiation of ................................................ 20, 23,
25 Preventive therapy ........................................... 41, 65,
66 Regimen options for children and adults ..............................
67 Supplement 2--Diagnosis and treatment for latent TB infection and active
TB ................................ 59-68 Treatment for active TB ...........................
12, 20, 24, 25, 66-68 Triage ...................................................
7, 11, 16, 25, 47 Tuberculin skin test (see PPD testing) Ultraviolet germicidal
irradiation (UVGI) .......... 7, 26, 30-32, 69, 88-95 Activation of HIV
gene promoters ..................................... 91 Applications .................................................
32, 89, 90 Autopsy rooms ........................................................
51 Carcinogenicity ......................................................
91 Definition ...........................................................
89 Determining maximum permissible exposure times ................... 92,
93 Duct irradiation ............................................. 32, 89,
94 Educating HCWs .......................................................
92 Effectiveness .....................................................
88-91 Exposure criteria for UV radiation ...............................
92, 93 HCW training issues ..................................................
92 In ambulatory-care settings ..........................................
89 Installation ................................................. 32, 33,
92 Labelling and posting caution signs .............................. 93,
94 Limitations ...................................................... 90,
91 Maintenance .......................................... 32, 33, 91, 94,
95 Monitoring ...........................................................
95 Obtaining consultation before installation ...........................
92 Precautions .......................................................
91-94 Recommended exposure limits (RELs) ................................
91-93 Safety issues ........................................................
91 Upper-room air irradiation ........................... 30, 32, 89, 90,
94 UV radiation, definition .............................................
89 Ventilation Air changes per hour (ACH) ....... 21, 29, 30, 51, 70, 72,
75, 84, 87, 90 Airflow patterns .......................... 69, 73-75, 78,
79, 85, 89, 90 Ambulatory-care areas ................................................
26 Anterooms .................................................... 30, 50,
77 Autopsy rooms ........................................................
51 Correction facilities ................................................
52 Dilution and removal .......................................... 69,
72-74 Direction of airflow ............................... 7, 32, 69, 73,
76-81 Discharge from booths, tents, and hoods .......... 32, 70, 71, 73,
81, 91 Emergency department .................................................
32 Emergency medical services ....................................... 51,
52 Enclosing devices ........................................ 31, 69, 75,
77 Engineers ................................................ 31, 69, 75,
77 Evaluation ............................................ 9, 19, 31, 69,
85 Exhaust ............. 7, 20, 21, 29, 30, 32, 35, 51, 69-78, 81-84, 88,
91 General ventilation ............ 7, 20, 26, 29-32, 69, 73, 74, 76, 78,
81 ................................................... 82, 84, 85, 87,
89 HEPA filter installation, maintenance, and monitoring .... 32, 81, 85,
86 Home-health-care settings ........................................ 53,
54 Hospices .............................................................
52 Local exhaust ventilation ............................. 7, 21, 35, 69,
70 Discharge exhaust ............................................. 71,
73 Enclosing devices ............................................. 70,
71 Exterior devices ..................................................
71 Maintenance .................................. 13, 19, 21, 30, 69, 85,
86 Monitoring ................................................ 21, 29,
78-81 Mixing factor ....................................................
72, 75 Negative pressure ..................... 21, 29, 51, 69, 76, 77-82,
86, 87 Operating rooms .............................................. 35,
50, 51 Periodic evaluation ..................................................
69 Positive-pressure rooms ..............................................
35 Pressure-sensing devices ...................................... 79-81,
85 Pressurizing the corridor in induce negative pressure ................
78 Radiology department ............................................. 28,
32 Rates (see Air changes per hour [ACH]) Recirculation of HEPA filtered
air ................... 32, 51, 78, 82, 83 Fixed .........................................................
83, 84 Portable ......................................................
84, 85 Re-entrainment ...................................................
87, 88 Short-circuiting ............................................. 71,
74, 75 Single-pass system ...................................................
73 Source control methods ..................................... 7, 69,
70-73 Stagnation ........................................................
74-76 Supplement 3--Engineering issues in TB control ....................
69-95 TB isolation rooms ......... 13, 21, 26-29, 31, 32, 69, 73, 76, 81,
86-88 Tents and booths (see Local exhaust ventilation) Treatment rooms
................... 29, 30, 69, 73, 76, 80-82, 86, 87, 89 Ventilation rates
.................................... 29, 74, 84, 87, 90 Waiting-rooms areas
.................................. 26, 31, 32, 53, 55 Very low-risk area
or facility ....................... 9, 11, 16, 30, 61, 62 Visitors .................................................................
2 Contact investigation ............................................ 48,
57 Pediatric patients ...................................................
27 Protection against UVGI ..............................................
33 Respiratory protection for .............................. 28, 31, 34,
102 Waiting-room areas ....................... 5, 20, 26, 31, 32, 53, 55,
89, 90 Workplace reassignment ..............................................
37, 38 Workplace restrictions ..............................................
40, 41 Active TB ............................................................
41 Extrapulmonary TB ....................................................
41 Latent TB infection ..................................................
40 Nonadherence to preventive therapy ...................................
41 Nonadherence to treatment ............................................
41 Return to work ................................................... 40,
41
List of Tables
Table 1. Elements of a risk assessment of tuberculosis (TB) in health-care
facilities ............................................. 9 Table 2. Elements
of a tuberculosis (TB) infection-control program ..... 12 Table 3. Characteristics
of an effective tuberculosis (TB) infection-control program ............................................
20 Table 4. Examples of potential problems that can occur when identifying
or isolating patients who may have infectious tuberculosis (TB).......
46 Table S2-1. Summary of interpretation of purified protein derivative
(PPD)-tuberculin skin-test results ...................................
62 Table S2-2. Regimen options for the treatment of tuberculosis (TB) in
children and adults ............................................... 67
Table S2-3. Dosage recommendations for the initial treatment of tuberculosis
in children and adults ............................... 68 Table S3-1. Air
changes per hour (ACH) and time in minutes required for removal efficiencies
of 90%, 99%, and 99.9% of airborne contaminants .........................................................
72 Table S3-2. Hierarchy of ventilation methods for tuberculosis (TB) isolation
rooms and treatment rooms .................................. 86 Table S3-3.
Maximum permissible exposure times for selected values of effective irradiance
................................................. 93
List of Figures
Figure 1. Protocol for conducting a tuberculosis (TB) risk assessment
in a health-care facility ...............................................
10
Figure 2. Protocol for investigating purified protein derivative (PPD)-tuberculin
skin-test conversions in health-care workers (HCWs) .... 44 Figure S3-1.
An enclosing booth designed to sweep air past a patient who has active
tuberculosis and entrap the infectious droplet nuclei in a high-efficiency
particulate air (HEPA) filter ................... 71 Figure S3-2. Room
airflow patterns designed to provide mixing of air and prevent passage
of air directly from the air supply to the exhaust ... 75 Figure S3-3.
Smoke-tube testing and anemometer placement to determine the direction
of airflow into and out of a room ...................... 79 Figure S3-4.
Cross-sectional view of a room showing the location of negative pressure
measurement ..................................... 80 Figure S3-5. Fixed,
ducted room-air recirculation system using a high-efficiency particulate
air (HEPA) filter inside an air duct ..... 83 Figure S3-6. Fixed ceiling-mounted
room-air recirculation system using a High-effeciency particulate air (HEPA)
filter ...................... 83 Figure S3-7. Air recirculation zone created
by wind blowing over a building .............................................................
88
Appendix B
Smoke-Trail Testing Method for Negative pressure Isolation Room
Test Method Description:
One of the purposes of a negative pressure TB isolation room is to prevent
TB droplet nuclei from escaping the isolation room and entering the corridor
or other surrounding uncontaminated spaces. To check for negative room
pressure, use smoke-trails to demonstrate that the pressure differential
is inducing airflow from the corridor, through the crack at the bottom
of the door (undercut) and into the isolation room. When performing a smoke-trail
test follow these recommendations where applicable:
1. Test only with the isolation room door shut. If not equipped with
an anteroom, it is assumed that there will be a loss of space pressure
control when the isolation door is opened and closed. It is not necessary
to demonstrate direction of airflow when the door is open.
2. If there is an anteroom, release smoke at the inner door undercut,
with both anteroom doors shut.
3. In addition to a pedestrian entry, some isolation rooms are also
accessed through a wider wheeled-bed stretcher door. Release smoke at all
door entrances to isolation rooms.
4. So that the smoke is not blown into the isolation room, hold the
smoke bottle/tube parallel to the door so the smoke is released perpendicular
to the direction of airflow through the door undercut.
5. Position the smoke bottle/tube tight to the floor, centered in the
middle of the door jamb and approximately two inches out in front of the
door.
6. Release a puff of smoke and observe the resulting direction of airflow.
Repeat the test at least once or until consistent results are obtained.
7. Minimize momentum imparted to the smoke by squeezing the bulb or
bottle slowly. This will also help minimize the volume of smoke released.
8. Depending on the velocity of the air through the door undercut, the
smoke plume will either stay disorganized or it will form a distinct streamline.
In either case, the smoke will directionally behave in one of three ways.
It will:
a. go through the door undercut into the isolation room,
b. remain motionless, or
c. be blown back into the corridor.
Compliance with the intent of the CDC Guidelines for negative pressure
requires that the smoke be drawn into the isolation room through the door
undercut.
9. Release smoke from the corridor side of the door only for occupied
TB isolation rooms. If the room is unoccupied, also release smoke inside
the isolation room (same position as in Step No. 5) to verify that released
smoke remains contained in the isolation room (i.e., smoke as a surrogate
for TB droplet nuclei).
10. If photography is performed or videotaping, it is recommended that
a dark surface be placed on the floor to maximize contrast. Be aware that
most autofocusing cameras cannot focus on smoke.
Testing "As Used" Conditions:
Testing of negative pressure isolation rooms requires that the test
reflect "as-used" conditions. Consider the following use variables which
may affect space pressurization and the performance of the negative pressure
isolation room:
1. Patient toilet rooms are mechanically exhausted to control odors.
The position of the toilet room door may affect the pressure differential
between the isolation room and the corridor. Smoke-trail tests should be
performed with the toilet room door open and the toilet room door closed.
This will not be necessary if the toilet room door is normally closed and
controlled to that position by a mechanical door closer.
2. An open window will adversely affect the performance of a negative
pressure isolation room. If the isolation room is equipped with an operable
window, perform smoke-trail tests with the window open and the window closed.
3. There may be corridor doors that isolate the respiratory ward or
wing from the rest of the facility. These corridor doors are provided in
the initial design to facilitate space pressurization schemes and/or building
life safety codes. Direct communication with the rest of the facility may
cause pressure transients in the corridor (e.g., proximity to an elevator
lobby) and affect the performance of the isolation room. Perform isolation
room smoke-trail testing with these corridor doors in their "as-used" position
which is either normally open or normally closed.
4. Isolation rooms may be equipped with auxiliary, fan-powered, recirculating,
stand alone HEPA filtration or UV units. These units must be running when
smoke-trail tests are performed.
5. Do not restrict corridor foot traffic while performing smoke-trail
tests.
6. Negative pressure is accomplished by exhausting more air than is
supplied to the isolation room. Some HVAC systems employ variable air volume
(VAV) supply air and sometimes VAV exhaust air. By varying the supply air
delivered to the space to satisfy thermal requirements, these VAV systems
can adversely impact the performance of a negative pressure isolation room.
If the isolation room or the corridor is served by a VAV system you should
perform the smoke test twice. Perform the smoke test with the zone thermostat
thermally satisfied and again with the zone thermostat thermally unsatisfied
thus stimulating the full volumetric flowrate range of the VAV system serving
the area being tested.
Smoke:
Most smoke tubes, bottles and sticks use titanium chloride (TiCl(4))
to produce a visible fume. There is no OSHA PEL or ACGIH TLV for this chemical
although it is a recognized inhalation irritant. Health care professionals
are concerned about releasing TiCl(4) around pulmonary patients. The smoke
released at the door undercut makes only one pass through the isolation
room and is exhausted directly outside. Isolation room air is typically
not "recirculated."
The CDC in the supplementary information to the 1994 TB Guidelines has
indicated that "The concern over the use of smoke is unfounded." Controlled
tests by NIOSH have shown that the quantity of smoke that is released is
so minute that it is not measurable in the air. Nonirritating smoke tubes
are available and should never-the-less be utilized whenever possible.
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