Number of Sexual Partners, Condom Use and Risk of Human Immunodeficiency Virus Infection

It remains to be clearly established how multiple sex partners affect the risk of HIV infection. Northern Italy is a region where the prevalence of HIV infection is high mainly among IV drug users. The authors conducted a case-control study nested in a cross-sectional survey among subjects attending three STD clinics in Bergamo Brescia and Verona with the goal of analyzing the relationship between the number of sex partners selected sex practices and the risk of HIV infection. The study population was comprised of 1259 males and 452 females who referred themselves for the first time between September 1988 and March 1993 to the clinics for suspected STD or STD treatment. The men were of median age 30 years in the range of 16-70 while the women were of median age 28 years in the range of 16-61. 113 males and 32 females were HIV-seropositive. In comparison with subjects reporting no or one sex partner over the three years before the interview the estimated odds ratio (OR) of HIV serum positivity were 1.2 0.8 and 0.3 in subjects reporting 2-3 4-5 and 6 or more partners respectively. The risk of HIV infection therefore does not increase linearly with the number of sex partners in this population. These results were similar considering separately males and females and among the 91 men reporting only homosexual partners. 165 men reported themselves as being bisexual. Regular condom use decreased the risk of HIV infection such that the OR of HIV infection was 0.5 for regular users compared to subjects who reported no or occasional use of condoms. Considering men only compared with men with no homosexual intercourse the OR of HIV infection was 2.3 among those reporting bisexual intercourse and 2.2 among men reporting only homosexual intercourse. There was no relation between HIV infection risk and receptive anal sex. IV drug use was strongly associated with HIV-seropositivity while a history of STD was more frequently reported by HIV-positive subjects than by HIV-negative subjects.