Risk factors for reactivation of tuberculosis in Manitoba.

Although rates of reported cases of active tuberculosis have been declining in Manitoba and throughout Canada over the past two decades, the percentage of active cases due to reactivated tuberculosis has remained relatively constant. From 1976 to 1981, 113 cases of reactivated tuberculosis were listed in the Manitoba tuberculosis registry. We found that 36 cases did not meet our criteria for reactivation, primarily because there was no 6-month period of inactivity; another 5 cases could not be verified. In more than half of the remaining 72 the initial episode had occurred before 1960. We also randomly selected from the registry as controls 118 age- and sex-matched cases of nonreactivated tuberculosis. We found that registered Indian status was significantly associated with risk of reactivation, especially when the initial disease had been extensive. Awareness of high-risk groups, earlier diagnosis and adequate treatment are needed to prevent reactivated tuberculosis.