Prevalence of HIV antibodies in groups at risk in Zürich, Switzerland.

The prevalence of HIV antibodies in various groups at risk was studied in 1,546 persons in Zürich. The prevalence was 17% (39/236) in homosexual men, 7% (13/180) in bisexual men, and 45% (14/31) and 42% (22/53) in female and male intravenous drug abusers, respectively. Heterosexual transmission appeared to be the route of infection in four seropositive persons (two women and two men) who had no homosexual contacts and were not drug abusers (4/1050).