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

Presented in part at the American Academy of Family Physicians 50th Annual Scientific Assembly, September 16-20, 1998, San Francisco, Calif.
https://doi.org/10.1067/mic.2000.103555Get rights and content

Abstract

Objectives: We investigated the risk of tuberculosis transmission from a person 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 potential exposure to Mycobacterium tuberculosis . The subjects were advised to undergo Mantoux tuberculin skin testing within the required time period to assess a conversion. In addition, information regarding tuberculosis history and other sources of potential exposure was solicited by means of a questionnaire. 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 first test (induration > 10 mm). Thirteen subjects with negative results refused further testing; 11 (28%) of the remaining 39 exhibited the booster phenomenon on the second test. Subjects who exhibited the booster phenomenon were significantly more likely to have received previous BCG vaccination. Nine contacts with negative results on the initial test had positive results on a third test administered at 12 weeks after the flight exposure Of these, 6 contacts had previous BCG vaccination, old tuberculosis, or a family member with tuberculosis; the remaining 3 reported on other risk factors for positive reactions. None of these 3 contacts had sat in the same section of the plan as the index patient. Conclusions: The 2-step tuberculin testing procedure is an effective tool for minimization of the booster effect, thus allowing accurate monitoring of subsequent tuberculin conversion rates. Moreover, the clustering of tuberculin skin test conversions among passengers in this study demonstrates the possible risk of M tuberculosis transmission during air travel. (AJIC Am J Infect Control 2000;28:233-8)

Section snippets

Methods

In October 1997, a US county health department notified the Taiwan Ministry of Foreign Affairs that highly infectious TB had been diagnosed in a passenger on a commercial airplane flight in September 1997. The index patient was a 44-year-old Taiwanese woman who, according to her physician in the county health department, had been receiving anti-TB medication for approximately 1 month at the time of the flight. Hospital evaluation revealed extensive pulmonary disease with cavitary lesions (Fig

Results

Of the 308 passenger and crew contacts on the flight, 31 (10.1 percent) were not notified; 25 of these were not residents of Taiwan, and the other 6 could not be located. The remaining 277 contacts (89.9%) resided in Taiwan and were notified of their possible exposure; of these, 225 (81.2%) responded. One hundred seventy-three subjects (76.9%) had positive tuberculin skin test results on initial testing (Table 1).Of the remaining 52 subjects, 39 received second tuberculin skin tests (the other

Discussion

It is now reasonably certain that TB is acquired through inhalation of tubercle bacilli in aerosolized respiratory secretions from infectious persons who talk, cough, or sneeze. A single cough or 5 minutes of talking by such a person may produce 3000 infectious units.10 The incident described here provided opportunities for investigation of the transmission of M tuberculosis on an airplane and further exploration of this concept of transmission. Our investigation was the first to use 2-step

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    *

    Reprint requests: Pair Dong Wang, Deputy Superintendent, Taipei Municipal Chronic Disease Hospital, No. 530, Lin-Shan N. Road, Taipei, Taiwan.

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    Copyright © 2000 Association for Professionals in Infection Control and Epidemiology, Inc. Published by Mosby, Inc. All rights reserved.