Epidemiologic studies of lung disease due to mycobacteria other than Mycobacterium tuberculosis in Japan

The incidence of lung disease due to mycobacteria other than Mycobacterium tuberculosis (atypical mycobacteria) in Japan was estimated to be 0.9--1.9 per 10(5) population per year in 1971--1979. Although the incidence of lung tuberculosis is steadily decreasing, the incidence of lung disease due to atypical mycobacteria has remained at almost the same level. The number of patients newly infected per year in recent years was calculated to be approximately 2,000. The ratio of the number of patients with lung disease due to atypical mycobacteria to the number of patients with lung disease due to atypical mycobacteria to the number of patients with lung disease due to all species of mycobacteria was highest in hospitals on the southwest coast of the Pacific. The atypical mycobacteria that caused disease most frequently belonged to the Mycobacterium avium-intracellulare complex. Of the 537 cases of disease due to atypical mycobacteria, 491 (89.6%) were due to these organisms; 43 (8.0%), to Mycobacterium kansasii; and 7 (1.3%), to Mycobacterium fortuitum. The disease due to M. kansasii appeared most frequently in hospitals in the Tokyo and Kanagawa prefectures. Patients with lung tuberculosis had a high risk of lung infection due to M. avium-intracellulare. The incidence of such disease in tuberculous patients was estimated to be 18.7 per 10(5) population per year, a rate that is approximately 10 times that found in the general population.