Objectives: An investigation was conducted to determine whether ongoing transmission of Mycobacterium tuberculosis was occurring in a California state prison.
Method: Prison pharmacy records were used to identify cases of active tuberculosis (TB).
Results: Ten of the 18 cases of active TB treated at the facility during 1991 were diagnosed at the prison that same year (an incidence of 184 per 100,000). Three inmates were infectious for a total of 7 months while imprisoned. The prevalence of TB skin test-positivity among inmates was 30%, and the incidence of new infection attributable to incarceration was 5.9 per 100 inmates per year.
Conclusions: Transmission of M. tuberculosis may be occurring in the California prison system.