Hepatitis C virus infection among sexually promiscuous groups and the heterosexual partners of hepatitis C virus infected index cases.

To define the role of sexual transmission in the spread of hepatitis C virus (HCV) infection, a seroprevalence study of antibodies against HCV was performed in populations at high risk for sexually transmitted diseases. Subjects included 310 female prostitutes, 88 clients of prostitutes, 168 homosexual men and 147 stable heterosexual partners of index cases reactive for anti-HCV (98 of whom were partners of drug addicts coinfected with HCV and human immunodeficiency virus [HIV]). All subjects denied prior transfusion or intravenous drug use. Controls were 400 voluntary blood donors selected randomly from first-time donors. The prevalence of anti-HCV by enzyme immunoassay, confirmed by a second-generation recombinant immunoblot assay, was 6.4% in prostitutes, 6.8% in clients of prostitutes, 4.2% in homosexual men, 7.4% in heterosexual partners of index cases and 1.2% in random donors. However, the anti-HCV prevalence in stable heterosexual partners of HCV-positive/HIV-positive index cases was 2.2 times higher than in stable heterosexual partners of index cases reactive for anti-HCV only (9.2% vs. 4.1%), and sexual partners of index cases coinfected with HCV and HIV were almost three times more likely to be infected with HIV than with HCV (25.5% vs. 9.2%). These data suggest that HCV infection may be sexually transmitted but with low efficiency and that this efficiency could be increased in the presence of coexistent HIV infection in the index case.