Risk factors for hepatitis B virus infection among homosexual men attending a sexually transmitted diseases clinic in Italy.

Prevalence of and risk factors for hepatitis B virus (HBV) infection were determined among 252 homosexual men with no history of intravenous drug use (median age 33 years, range 18-77) treated at a sexually transmitted disease (STD) clinic in Rome. The overall prevalence of antibodies to HBV core antigen (anti-HBc) was 50.8%, a rate nearly nine times as high as the 5.8% found recently in a national sample of young male adults, aged 18-26 years, and twice as high as the 22% found in heterosexuals attending the same clinic over the same period of time. Multiple logistic regression analysis showed that the risk of anti-HBc positivity was independently associated with increasing age, five or more sexual partners in the previous year, positive HIV serology and positive syphilis serology. Lower level of schooling, lack of condom use, history of non-ulcerative STD, current or past history of genital herpes, and positive anti-HCV serology were not associated with anti-HBc positivity. These findings corroborate the importance of sexual transmission of HBV in homosexual men. Behavioural factors, such as multiple sexual partners, probably enhance the efficiency of this mode of HBV transmission.