Components of the epidemiologic investigation included tuberculinskin-test screening and collection of demographic information for students exposed to a driver with tuberculosis, chestradiography and medical evaluation of individuals with positive skin tests, and DNA fingerprinting of M tuberculosis isolates. A positive skin test was defined as >/=10 mm induration, and a converter was an individual with an increase in reaction size of >/=10 mm in the past 2 years.
RESULTS:
The rates of positive skin tests were 0.8 percent, 0.3 percent, 9.9 percent, 1.1 percent and 0.7 percent among US-born student exposed to drivers 1 through 5, respectively. The relative risk for a positive tuberculinskin test was significant only for student expose to driver 3 and the only secondary case identified among students was exposed to driver 3. The DNA fingerprinting patterns of isolates from drivers 3 and 4 matched.