Two-step tuberculin testing of passengers and crew on a commercial airplane

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.