Factors for the onset of and the exacerbation of tuberculosis. 6. Recent socio-medical characteristics of tuberculosis and their perspectives in Japan

In the late 1970s the decline of TB incidence rate has begun to slow down among both elderly population and younger one. This phenomenon mostly owed the reactivation of dormant M. tuberculosis infection among the elderly people and small TB outbreaks in the younger generation. The micro-epidemics among adolescent and young adults have been reported since 1980. The latest data showed the TB incidence in 1997 was 33.9 per 100,000 population, increased from 33.7 per 100,000 in 1996. To explain the situation above, several sociomedical factors were discussed as follow: (1) Age distribution of TB: The highest peak of newly registered TB patients shifted to the elder age cohorts and was the age group between 65 and 74 years in 1997, contrasting small peaks observed in 20-29 years age group remained unchanged. (2) Characteristics of infection route: Overall incidence rates of smear positive TB cases slightly increased in 1980s and leveled off thereafter. However, the number of smear positive cases among persons elder than 70 years old sharply increased, 1,779, 3,744, 5,728, in 1977, 1987 and 1997, respectively. Several papers showed that about one quarter of TB patients was diagnosed as TB while being treated for diseases other than TB. This may have contributed to the current TB infection. (3) Delay in case-finding: Patient's delay in symptomatic smear positive cases, especially among male patients in 30-54 age group, has been increased during last 10 years. This may also contribute to the current TB issue to the younger people. (4) TB problems in the cities: TB incidence rate in a certain area of some big cities was much higher than the other areas and the regional difference became magnificent due to serial socioeconomic problems of vulnerable population there. (5) Notification of TB: One study using mailed questionnaires showed that only 76 percent of medical doctors knew the TB notification system under the TB control law. It concluded that contact tracing would become more important issue in case-finding and the 100 percent of TB notification in medical institutions would be indispensable.