Public health aspects of relapsing tuberculosis.

It was possible to assess the problem of relapse of pulmonary tuberculosis in Denmark from a public health point of view since, in 1950, it became obligatory to report to a national register all arrest of disease among patients with active pulmonary tuberculosis. A uniform criterion for arrest was used. Relapse rates were studied among 6,242 persons whose disease was arrested during 1951–1953. A total of 522 relapses were reported during a seven-year follow-up period. Rate of relapse was 13 per 1,000 person-years, 50 times higher than the incidence of new cases in the general population. The rate was higher in males than in females and increased considerably with age. Frequency of relapse was higher among infectious than among noninfectious patients. Rate of relapse decreased during the first part of the observation period but then levelled off. The relapse rate in the study population was twice as high as among patients from the isoniazid era. The excess mortality, which is based on deaths from all cause...