Transmission of tuberculosis (III)

Abstract

Tuberculosis outbreak is defined as group infection more than 20 persons had been infected with tubercle bacilli in Japan, provided one person developed disease is counted as 6 persons had been infected. Outbreak is to be reported compulsory to the Ministry of Health, Welfare and Labor. A total of 365 outbreaks of tuberculosis have been reported in these 10 years during 1994 and 2004. Out of them, large scale outbreak more than 10 persons have developed disease were 41 (11.2%). Results of contact surveys has reported that 0.36% of newly registered smear positive cases had caused tuberculosis outbreak, 1.1% had resulted small scale group infection (5 to 19 persons had been infected), although majority of the bacteriology positive cases didn't infected even one person. To make clear the mode of airborne infection with tubercle bacilli more clearly, the author has discussed the results of quantitative model on droplet nucle infection by Riley RL and others, nosocomial infection of smallpox virus in Germany in 1970, the results of analysis of airflow at the sites of outbreaks at business office and middle school in Japan, and so on. Finally, the author has reviewed the development of research on annual risk of tuberculosis infection in Japan and discussed about the present problems of risk of tuberculosis infection in Japan.