Epidemiological investigation of a varicella outbreak in an Italian prison.

Five cases of varicella occurred in a women's prison in Rome. A serosurvey conducted in the prison found that 14.5% of the inmates were susceptible. The sensitivity and positive predictive value of a history of varicella were high, whereas specificity was rather low. The attack rate among susceptible inmates was approximately 22%. Preventive measures probably contributed to reduce infection spread.