An epidemic of primary tuberculosis in a Canadian aboriginal community

In 1987, an outbreak of primary tuberculosis occurred in a Canadian aboriginal community of 350 people. The source case was a young woman who had been symptomatic for four months with smear positive cavitary pulmonary tuberculosis. Her 17 siblings and their families were frequent close contacts. Among the 626 persons surveyed in the community and environs, 35 additional active cases of tuberculosis were identified. The mean age of cases was 13 years and the median age 10 years. The method of diagnosis was bacteriological in 20 and radiological in 16. There were 257 positive tuberculin reactors of whom 120 had no previous record of a positive skin test. Isoniazid prophylaxis was recommended to all new reactors, close household contacts, reactors under the age of 35 years and reactors with lung scars. One late case was identified at one year of follow-up in a contact who had refused prophylaxis. The rates of infection and disease were higher in the family (65% and 46%, respectively) than in the community and environs (19% and 5.6%, respectively). This report illustrates the nature of a point source epidemic of primary tuberculosis in a susceptible community with a predictable reservoir of infection. The delay in diagnosis of the source case allowed numerous new infections to occur. However, prompt aggressive contact follow-up was successful in containing the epidemic. To prevent future outbreaks, the reservoir of infected persons must be identified and administered chemoprophylaxis.