Sexual transmission of hepatitis C virus: cohort study (1981-9) among European homosexual men.

OBJECTIVE To determine the prevalence, incidence, and persistence of positivity for antibodies to hepatitis C virus (anti-HCV) and the potential for sexual transmission of the virus. DESIGN A cohort analysis covering 1981-9 comparing estimated cumulative incidences of and seroconversion rates for anti-HCV with those of hepatitis B core antibody (anti-HBc) and antibodies to the human immunodeficiency virus (anti-HIV). SETTING Copenhagen and Aarhus, Denmark. SUBJECTS 259 Male members of a Danish homosexual organisation. MAIN OUTCOME MEASURES Correlations of prevalence and incidence with a wide range of sexual lifestyle variables. RESULTS Only four (1.6%) subjects were positive for anti-HCV in 1981. The estimated cumulative incidence of positivity for anti-HCV was 4.1% in 1984 (seroconversion rate during 1981-4 (2.5%)) and remained at 4.1% in 1989 (seroconversion rate nil during 1984-9). In contrast, positivity for anti-HBC rose from 44.0% in 1981 to 52.7% in 1984 (seroconversion rate 15.5%) and 58.8% in 1989 (seroconversion rate 12.9%), and that for anti-HIV rose from 8.8% to 24.0% (seroconversion rate 16.7%) and 30.1% (seroconversion rate 8.0%) respectively. Three anti-HCV positive patients seroreverted three to five years later. None of the anti-HCV positive subjects had had a transfusion and only one gave a past history of intravenous drug use. Variables in sexual lifestyle correlated with the presence of anti-HBc but not with that of anti-HCV. CONCLUSIONS In contrast with hepatitis B virus and HIV, sexual transmission of hepatitis C virus seems to be a rare event. Furthermore, antibodies to the virus may become undetectable after several years.