Twenty-year trend of chronic excretors of tubercle bacilli based on the nationwide tuberculosis prevalence surveys in Korea, 1975-1995.

SETTING

A study of chronic excretors of tubercle bacilli (chronic cases) based on the nationwide random sample surveys of tuberculosis prevalence conducted in Korea from 1975 through 1995.

OBJECTIVE

To investigate the temporal trend of the prevalence of chronic cases, and to match these with treatment outcomes and drug resistance rates.

DESIGN

Bacillary cases were classified by history of chemotherapy into new (those who denied a history of chemotherapy), non-chronic (those who had taken chemotherapy for less than 2 years) and chronic cases (those who had taken chemotherapy for more than 2 years).

RESULTS

Chronic cases decreased from 107 to 12 per 100000 population (annual rate of reduction [ARR] 11.89%) over the 20-year period. The ARR of chronic cases was significantly greater than that of new cases, and accelerated from 1985 (ARR 15.83%), after the application of short course chemotherapy. Rates of overall drug resistance rates increased up to 1980, and those of multidrug resistance up to 1985, followed by a decrease thereafter. A reduction in chronic cases was observed even during the period of increase in drug resistance (including multidrug resistance).

CONCLUSION

The prevalence of chronic tuberculosis cases has decreased due to improvements in overall treatment outcome.