Objectives: We investigated the risk of tuberculosis transmission from a pe
rson with highly infectious pulmonary tuberculosis to fellow passengers and
crew members on a 14-hour commercial flight. The 2-step tuberculin testing
was used to minimize the effects of the booster phenomenon.
Methods: Passengers and flight crew members identified from airline records
were contacted by letter, telephone, or both to notify them of their poten
tial exposure to Mycobacterium tuberculosis. The subjects were advised to u
ndergo Mantoux tuberculin skin testing within the required time period to a
ssess a conversion. In addition, information regarding tuberculosis history
and other sources of potential exposure was solicited by means of a questi
onnaire.
Results: Of the 277 passengers and crew members on the aircraft, 225 (81.2%
) responded. Of these, 173 (76.9%) had positive tuberculin results on the f
irst test (induration > 10 mm). Thirteen subjects with negative results ref
used further testing; 11 (28%) of the remaining 39 exhibited the booster ph
enomenon on the second test. Subjects who exhibited the booster phenomenon
were significantly more likely to have received previous BCG vaccination. N
ine contacts with negative results on the initial test had positive results
on a third test administered at 12 weeks after the flight exposure Of thes
e, 6 contacts had previous BCG vaccination, old tuberculosis, or a family m
ember with tuberculosis; the remaining 3 reported on other risk factors for
positive reactions. None of these 3 contacts had sat in the same section o
f the plan as the index patient.
Conclusions: The 2-step tuberculin testing procedure is an effective tool f
or minimization of the booster effect, thus allowing accurate monitoring of
subsequent tuberculin conversion rates. Moreover, the clustering of tuberc
ulin skin rest conversions among passengers in this study demonstrates the
possible risk of M tuberculosis transmission during air travel.