[The 74th Annual Meeting Special Lecture. II. Present situation and problems of tuberculosis in Japan--its prevention, diagnosis and treatment].

1. Outline of tuberculosis epidemiology after the World War II Tuberculosis was surprisingly highly prevalent during the World War 2nd in Japan, and it was reported that the incidence of TB was as high as 698.4 in 1951. Strong TB control program has been carried out throughout the country after the new Anti-TB Law had been enacted in 1951. TB incidence decreased with the annual reduction rate of 11% up to 1976, it was one of the highest speed of TB decrease in the world. The decrease of TB is stagnating since 1977, and the incidence is still 33.9 in 1997. 2. Causes of stagnation of TB in Japan It is estimated that the annual risk of TB infection was so high as 4% in 1945 that many of the children had been infected with TB bacilli in those days. As a result, the majority of the people aged 60 years old or more at present are already infected with TB bacilli, and more than half of the new cases is being occurred among them at present in Japan. Moreover, the life span of those already infected people is extending so remarkably that the percentage of the aged is increasing and TB incidence is stagnating in Japan. The causes of the stagnation are not the spread of HIV infection or the increase of TB among the immigrants or refugees, because both of them are not so big problems in Japan. However, more severe problems of TB epidemiology in Japan are that 1. the incidence of smear positive cases didn't decrease more than these ten years, 2. the most marked stagnation of the incidence of TB is being observed among the young aged 20 to 39, 3. the incidence of TB in big cities doesn't decrease recently and 4. group infection and nosocomial TB infection is increasing recently. The author has analyzed the factors of the stagnation of TB in Japan, and come to the conclusions that it is caused by 1. the increase of the population by 3.0%, 2. the aging of the population by 41.0%, 3. the increase of compromised host (diabetes mellitus and so on) by 19.8%, and 4. other factors by 36.3%. It was considered that the main other factor is the marked stagnation of TB infection risk mainly by socioeconomic changes such as progressed urbanization and the spread of the modern housing with aluminum sash to increase the chances of TB infection in office buildings and/or private house. 3. Present problems of TB prevention, diagnosis and treatment in Japan As BCG vaccination is so widely and so repeatedly being carried out for children that the diagnosis of TB infection is almost impossible now in Japan. Accordingly the frequency and/or risk factors of TB infection in the community are not so clear. Preventive chemotherapy is given for high risk groups in Japan, but its diagnosis may become often unreliable. New techniques such as PCR, MTD, AccuProbe, RFLP and so on are used frequently in Japan, but the consideration on the false negative results of the examinations are lacking on occasion. The results of the cohort analysis of TB treatment among all the registered cases are rather satisfactory, but it was concluded that the shortening of the duration of the hospitalization and chemotherapy is advised if compared with those of Japan and those of the other developed countries.