Annual risk of tuberculous infection in Taiwan, 1994-1998

Tuberculosis is still an important public health issue in Taiwan, and monit oring the trend of annual risk of infection (ARI) with Mycobacterium tuberc ulosis is essential. In this study, we conducted tuberculin skin tests to e stimate the prevalence and annual risk of M. tuberculosis infection in firs t-grade schoolchildren in Taiwan Province. Because mass bacille Calmette-Gu erin (BCG) vaccination programs have been carried out here, only non-BGC-va ccinated students were tested. From September 1996 through June 1998, there were 520,866 registered first-grade elementary school students in Taiwan P rovince. Of them, 15,147 (2.9%) were non-BCG-vaccinated, as determined by t he absence of a BCG scar. All of them were tested for M. tuberculosis infec tion with 1 tuberculin unit (0.1 mL injection) of purified protein derivati ve RT23, by means of the Mantoux technique. Among the tested schoolchildren , 430 (2.8%) had a positive tuberculin reaction. Thus, the calculated ARI w as 0.44%. The ARI varied in different areas of Taiwan, being highest (1.04% ) in Nantou County and lowest (0.14%) in Miaoli and Tainan Counties. The AR I in aboriginal areas (1.16%) was 2.7 times that in nonaboriginal areas (0. 42%). Our results indicate that the M. tuberculosis ARI is still high in Ta iwan. To achieve the World Health Organization target of less than 0.1% for industrialized countries, we must intensify tuberculosis control programs in Taiwan.