RISK-FACTORS FOR TRANSMISSION OF MYCOBACTERIUM-TUBERCULOSIS IN A PRIMARY-SCHOOL OUTBREAK - LACK OF RACIAL DIFFERENCE IN SUSCEPTIBILITY TO INFECTION

Recent data have suggested that there are racial differences in the su sceptibility to infection by Mycobacterium tuberculosis. An opportunit y to test this suggestion was afforded by an outbreak of tuberculosis in a racially mixed elementary school in St, Louis County, Missouri, A physical education teacher was discovered to have cavitary pulmonary tuberculosis. Of 343 students in the school, 176 (51 percent) were fou nd to be tuberculin skin test positive (greater than or equal to 5 mm induration by Mantoux method); 32 children had abnormal chest radiogra phs. More frequent contact with the physical education teacher was ass ociated with infection (p < 0.001). Black children were no more likely to be infected than were white children (relative risk (RR) = 0.98, 9 5% confidence interval (CI) 0.78-1.22). However, black children who we re tuberculin positive had larger skin reactions than did white childr en (mean, 18.9 vs. 16.6 mm, p < 0.001) and were more likely to have ab normal chest radiographs (RR = 2.76, 95% CI 1.44-5.27). Among tubercul in-positive children, low body mass index (less than 10th percentile) was associated with active disease (RR = 2.90, 95% CI 1.45-5.80). The analysis of race was unchanged after controlling for sex, body build, and level of contact with the physical education teacher. Widespread t uberculous infection resulted from contact with a highly infectious st aff person. Thin body build was a risk factor for active disease. Blac k children were no more susceptible to infection than were white child ren, although they more commonly developed radiographic evidence of ac tive disease.