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 diag-
nosed as TB while being treated for diseases other than TB This may have contrib-
uted to the current TB infection.
(3) Delay in case-finding
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