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.