WHO guidelines to control airline-transmitted TB expensive and worthless
Mantoux tuberculin skin test; Image credit: CDC
In today’s blog Suvash Shrestha TLS Regional Advisor from Nepal writes on a review published in Lancet Infectious Diseases that has raised doubts on the efficacy and usefulness of WHO guidelines to control transmission of tuberculosis in airlines.
Of the total of 2,761 passengers screened after potential contact with a TB case, only 10 showed up positive for the tuberculin skin reaction test, which proved only latent infection by the tubercle bacilli.
Earlier in 2006 and 2008, WHO had recommended all airlines to trace and screen passengers, who have sat for longer than eight hours adjacent to a pulmonary tuberculosis-positive-person. The rule also prohibited an individual with TB from all commercial air travel until he or she is no longer infectious, as proved after two negative tests.
The review mentions that there is little danger of contagion from air travel. Ibrahim Abubakar of the University of East Anglia in eastern England looked into accounts of 41 events when tuberculosis was suspected to be transmitted by air travel. Of the total of 2,761 passengers screened after potential contact with a TB case, only 10 showed up positive for the tuberculin skin reaction test, which proved only latent infection by the tubercle bacilli. None became actively infected.
Thus, the report concluded that the screening was not necessary at all. Besides, the chances of TB transmission in an airplane is too less. In the first place, contagion with TB depends on several factors like the bacterial load in the sputum, duration and nature of contact, ventilation and finally the vulnerability of the exposed people. Those with impaired immune system due to cancer, AIDS or any other disease are vulnerable to get TB, but, luckily most travelers are relatively healthy. Thus, the chance of transmission remains low.
Next, most airliners have such highly efficient air filtration that germs even as small as 0.3 nanometers cannot get through. This means that Mycobacterium practically does not have any chance to get through. In addition, cabin air is generally renewed more than 15 times an hour. This is even more than the standard used in isolation rooms for multidrug resistant TB cases.
“Although an airline cabin is a closed confined space, the cumulative duration of exposure is relative short compared with households or…other modes of transport where individuals might travel on the same route daily,” Abubakar noted.
The evidences showed that WHO guidelines were baseless and not worth following. However, the report did not doubt the severity of the TB epidemic or the need to trace passengers in the event of a genuine emergency. “Resources might be better spent addressing other priorities of tuberculosis control and helping all achieve Millennium Development Goals related to tuberculosis.”