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Tuberculosis
Description
Mycobacterium tuberculosis is a rod-shaped
bacterium that can cause disseminated disease but is most frequently
associated with pulmonary infections. The bacilli are transmitted
by the airborne route and, depending on host factors, may lead to
active disease. Tuberculosis (TB) can usually be treated successfully
with multiple medications.
Occurrence
In many other countries, TB is much more common
than in the United States, and it is an increasingly serious public
health problem.
Risk for Travelers
To become infected, a person usually would have
to spend a relatively long time in a closed environment where the
air was contaminated by a person with untreated TB who was coughing
and who had numerous M. tuberculosis organisms (or tubercle
bacilli) in secretions from the lungs. TB infection is generally
transmitted through the air; therefore, there is virtually no danger
of its being spread by dishes, linens, and items that are touched,
or by most food products. However, it can be transmitted through
unpasteurized milk or milk products obtained from infected cattle.
Travelers who anticipate possible prolonged exposure
to TB (e.g., those who could be expected to routinely come in contact
with hospital, prison, or homeless shelter populations) should be
advised to have a tuberculin skin test before leaving the United
States. If the reaction is negative, they should have a repeat test
after returning. Because persons with HIV infection are more likely
to have an impaired response to the tuberculin skin test, travelers
with HIV infection should be advised to inform their physicians about
their HIV status. Except for travelers with impaired immunity, travelers
who already have a positive tuberculin reaction are unlikely to be
reinfected.
CDC and state and local health departments have
published the results of six investigations of possible TB transmission
on commercial aircraft. In these six instances, a passenger or a
member of a flight crew traveled on commercial airplanes while infectious
with TB. In all six instances, the airlines were unaware that the
passengers or crew members were infected with TB. In two of the instances,
CDC concluded that TB was probably transmitted to others on the airplane.
The findings suggested that the risk of TB transmission from an infectious
person to others on an airplane was greater on long flights (8 hours or
more). The risk of exposure to TB was higher for
passengers and flight crew members sitting or working near an infectious
person because they might inhale droplets containing TB bacteria.
Based on these studies and findings, WHO issued
recommendations to prevent the transmission of TB in aircraft and
to guide potential investigations. The risk of TB transmission on
an airplane does not appear to be greater than in any other enclosed
space. To prevent the possibility of exposure to TB on airplanes,
CDC and WHO recommend that persons known to have infectious TB travel
by private transportation (that is, not by commercial airplanes or
other commercial carriers), if travel is required. CDC and WHO have
issued guidelines for notifying passengers who might have been exposed
to TB aboard airplanes. Passengers concerned about possible exposure
to TB should be advised to see their primary health-care provider
for a TB skin test.
Prevention
Vaccine
The Bacille Calmette-Guerin (BCG) vaccine is used
in most developing countries to reduce the severe consequences of
TB in infants and children. However, BCG vaccine has variable efficacy
in preventing the adult forms of TB and is therefore not routinely
recommended for use in the United States and other developed countries.
Other
Travelers should be advised to avoid exposure to
known TB patients in crowded environments (e.g., hospitals, prisons,
or homeless shelters). Travelers who will be working in hospitals
or health-care settings where TB patients are likely to be encountered
should be advised to consult infection control or occupational health
experts about procedures for obtaining personal respiratory protective
devices (that is, N-95 respirators), along with appropriate fitting.
Additionally, TB patients should be educated and trained to cover
coughs and sneezes with their hands or tissues. Otherwise, no specific
preventive measures can be taken or are routinely recommended for
travelers.
Treatment
Persons who are infected or who become infected
with M. tuberculosis can be treated to prevent TB. Recent
data from the WHO suggest that isoniazid resistance is relatively
common in different parts of the world. If a traveler has a tuberculin
skin test conversion associated with international travel, consideration
should be given to the possibility of drug resistance. Updated American
Thoracic Society (ATS)/CDC recommendations for treatment of latent
TB infection suggest that 4 months of rifampin is a reasonable alternative
to isoniazid. In settings where multidrug-resistant TB is common,
experts in infectious diseases or pulmonary medicine should be consulted
to determine alternative treatment regimens. Travelers who suspect
that they have been exposed to TB should be advised to inform their
physicians of the possible exposure and receive appropriate medical
evaluation. CDC and the ATS have published updated guidelines for
targeted tuberculin skin testing and treatment of latent TB infection. [4]
— Kenneth
Castro, Michael Iademarco
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