results for 2 of 11 previously skin test-negative physicians and nurses in a prison infirmary converted to positive during the period November 1990 through March 1991 after exposure to a prisoner with active multidrugresistant tuberculosis (annual rate of infection, 6.4 percent) (Campbell et al., 1993). A report on two other outbreaks in 1995 and 1996 cited annual skin test conversion rates for previously negative employees of 2.8 percent for those exposed in one prison and 4.9 percent for those exposed in a second prison (Prendergast et al., 1999). No employees developed active tuberculosis.

A 1991 outbreak of tuberculosis among New York state prison inmates resulted in the transmission of M. tuberculosis to prison workers. The state then instituted a program of mandatory tuberculin skin testing for employees beginning in November 1991 (Steenland et al., 1997). For 1992, investigators concluded that approximately one-third of new tuberculosis infections among workers were due to occupational exposure, with higher rates for workers in prisons that reported cases of active disease among inmates. They suggested that 1992 was probably the peak year for transmission because the incidence of tuberculosis among prisoners dropped by about 40 percent during the next 3 years.

A report on a 1994 outbreak in a Texas prison found a clustering of cases of active tuberculosis including 15 cases in inmates and one case in a prison worker (an instructor in educational program) (Bergmire-Sweat et al., 1996). The report did not include skin test information for workers but found higher conversion rates for inmates in the wing on which the source case resided and for those having classes in the same classroom as the source case.

A recent outbreak in a South Carolina state prison is still being investigated, but investigators have indicated that a medical student exposed to infectious inmates developed active tuberculosis. A brief abstract describes the setting for this outbreak as a segregated dormitory for HIV-infected inmates (Spradling et al., 2000). Twenty-nine inmates in the population investigated developed active tuberculosis, and 26 of these inmates were housed in the same area of the segregated dormitory as the index case.

Prisons differ from hospitals in that they more often draw inmates from distant communities. For example, New York City residents convicted of violating state laws may be incarcerated in upstate prisons, whereas those convicted of violating federal laws may go to an out-of-state prison. Some prison systems actively seek to import prisoners from other states. For example, a private prison in Oklahoma, a state with a low prevalence of tuberculosis, has contracted to house prisoners from Hawaii, a high-prevalence state (Kakesako, 1998). Other inmates from Hawaii have gone to Minnesota and Tennessee prisons.

Although facilities that import prisoners may seek relatively low-risk offenders and screen them for tuberculosis and other medical problems,