Tuberculosis
Risk on Aircraft
The CDC has been involved in a
series of epidemiologic investigations related to the possibility of
transmission of tuberculosis (TB) on airlines. The most recent investigation,
published in the March 3, 1995 issue of the Morbidity and Mortality Weekly Report (MMWR), concluded that TB bacteria
were transmitted from an infectious passenger with active TB to four other
passengers during an eight and a half hour domestic airline flight.
While an earlier CDC study found that Mycobacterium tuberculosis was
transmitted from an infectious flight attendant to other crew members who had
spent significant time together, this incident is the first time that
transmission of the bacteria from one passenger to another has been found. None
of the passengers thought to be infected with TB during the flight has active
disease. The risk of transmission on a commercial aircraft is low. There is no
reason to suspect that the risk of transmission of TB on aircraft is greater
than in any other confined space including other forms of public transportation
if the duration is the same.
In the flight situation studied, transmission occurred because those in close
proximity to the passenger with active infectious TB inhaled tiny infectious
droplets produced when the infectious passenger coughed. The CDC did not study
the air filtration systems in the aircraft. However, according to the airplane
manufacturers, planes that recirculate air have HEPA (high-efficiency
particulate air) filters in their air handling systems. HEPA filters are able to
filter out TB bacteria from the air and are recommended by CDC for use in
hospitals to protect persons from TB. Also, according to the Department of
Transportation, the number of air exchanges per hour in airplanes exceeds the
number recommended for hospital isolation rooms which are used to isolate
persons with infectious TB.
To prevent possible exposure to TB aboard aircraft, CDC recommends that
persons known to have infectious TB should travel by private transportation
rather than commercial carrier, if travel is required. If an airline becomes
aware that someone with active infectious TB has flown on a flight longer than
eight hours, CDC suggests that the airline notify crew and passengers who may
have worked or been seated near to the passenger with infectious TB. Anyone who
is concerned about possible infection with TB should consult his/her primary
health care provider or local health department and have a TB skin test.
TB is a treatable and preventable disease. Once infected, a person's body may
harbor TB organisms for years, or for life, without progressing to active TB
disease. In certain cases of infection, preventive treatment is recommended to
prevent infection from progressing to disease.
In 1994, there were 24,361 cases of TB reported to the CDC, a 3.7% decrease
from the year before. However, there was a 20% increase in the number
of TB cases reported from 1985 to 1992 after a thirty year decline. The
resurgence of TB was due in part to the lack of public health attention
and resources directed toward this infectious disease that many believed
to be on the way to elimination. This latest study regarding TB is a reminder
of the importance of a sound national and international public health
system for surveillance and control of infectious diseases.
See the Diseases
section for more information on tuberculosis. |