Background: The role of sexual transmission of hepatitis C virus (HCV) infection is still not completely understood, partly because of the lack of longitudinal studies among cohorts of HCV-negative individuals who engage in at-risk sexual behavior.
Goals: To evaluate the incidence of HCV infection in a population at risk for human immunodeficiency virus type 1 (HIV-1) infection and other sexually transmitted diseases (STD) and to identify factors associated with HCV seroconversion.
Study design: A retrospective longitudinal study was carried out on a cohort of consecutive attendees of a voluntary HIV-1 testing and counseling program in a large STD center in Rome. All individuals undergoing at least two consecutive tests for HCV antibodies were enrolled. Clinical data and information on individual behavior were collected for all study participants.
Results: Between June, 1992 and December, 1994, a total of 709 individuals (12 intravenous drug users [IDU], 244 homosexuals, and 453 heterosexual non-IDUs), initially negative for HCV antibody, were tested more than once. Among these individuals, 15 HCV seroconversions occurred. The average follow-up time was 1.25 person/years (p/y) for an incidence rate of 1.69 per 100 p/y. The incidence rates by exposure category were 39.30 per 100 p/y among IDUs, 1.37 per 100 p/y among homosexual men, and 0.97 per 100 p/y among heterosexual non-IDUs. Excluding IDUs, of the 697 STD clinic attendees engaging in at-risk sexual behavior, HIV-1-positive status tended to be associated with HCV seroconversion (relative hazard = 5.48; 95% confidence interval = 0.85-35.40). The HCV crude incidence rates among HIV-1-infected patients at enrollment was 11.5%, 4.2%, and 2.4% in those with severe, moderate, and mild levels of immunosuppression, respectively (chi-square for trend = 2.38, P = 0.1).
Conclusions: In this cohort, HCV infection was confirmed to be strongly associated with intravenous drug use. Nonetheless, the occurrence of two thirds of the total HCV seroconversions in non-IDU individuals engaging in at-risk behavior suggests a role of sexual practices in the transmission of the infection. Among non-IDU individuals, the risk for development of HCV infection tended to increase in those who were HIV-1 infected.