High prevalence of antibodies to human immunodeficiency virus in heterosexual persons attending a sexually transmitted disease clinic in Italy.

The prevalence of antibodies to human immunodeficiency virus (anti-HIV-1) was determined in 924 outpatients attending a sexually transmitted disease clinic. The overall prevalence of anti-HIV-1 was 9%. Six of 14 intravenous drug addicts and 4 of 34 patients of African origin were anti-HIV-1 positive. In the other 876 patients, the anti-HIV prevalence was 6.6% in 467 heterosexual men, 5% in 261 heterosexual women and 22.3% in 148 homosexual or bisexual men. The prevalence of anti-HIV-1 in the heterosexual subjects was much higher than that expected in the general population and than that observed in patients attending sexually transmitted disease clinics in other developed countries. Intravenous drug abusers, who represent the most important group at risk for AIDS in Italy, could contribute to the spread of HIV infection through heterosexual contacts with persons without other known risk factors.