No cases of sexual transmission of hepatitis C virus were found in a three year San Francisco study published in the January 2004 edition of Sexually Transmitted Diseases. The study, conducted amongst repeat HIV testers, the overwhelming majority of whom were gay men, also failed to find any association between unprotected anal sex and new hepatitis C infections. These findings stand in contrast to a recent observational study conducted in the UK that found that unprotected anal sex was the sole common risk factor for hepatitis C transmission amongst HIV-positive gay men (see link to this and other recent news stories on the sexual transmission of hepatitis C below).
Investigators from San Francisco conducted a retrospective study involving 981 repeat HIV testers between 1997 and 2000. The investigators aimed to establish the prevalence of hepatitis C infection amongst this population and the incidence of new hepatitis C infections.
The overwhelming majority of individuals included in the analysis were gay men (754 people, 77%), 135 (1%) were women and 92 (15%) were heterosexual men.
A total of 576.6 person years of observation were contributed by the 703 individuals who had blood samples for both HIV tests. There were no new cases of hepatitis C detected giving a hepatitis C incidence of zero. However, six new cases of herpes simplex virus-2 (HSV-2) and ten new HIV infections occurred (incidence rates 2.8 per 100 person years and 1.8 per 100 person years respectively).
The hepatitis C prevalence was 2.5%, and was highest in heterosexual men (4.3%), followed by heterosexual women (3.7%). The prevalence in gay men was 2.1%. Univariate analysis showed that individuals with a history of injecting drug use were over 33 times more likely to be infected with hepatitis C than individuals with no history of injecting drugs.
Gay men over 50 years of age were more likely to be infected with hepatitis C than gay men aged under 30 (odds ratio 6.6; 95% CI, 1.2 - 44.0). HIV-positive gay men were also more likely to be hepatitis C-positive than gay men who were not infected with HIV (odds ratio 5.4; 95% CI, 1.2 - 19.1).
No statistically significant association was found between recent sexual risk behaviour, including either insertive or receptive unprotected anal sex and hepatitis C infection. However, an association was found with increasing age (p=0.01), but not for the number of lifetime sexual partners (p=0.35).
In multivariate analysis, age 50 or above (odds ratio 8.5; 95% CI, 2.6 ?27.7), HIV infection (odds ratio, 5.7; 95% CI, 1.6 - 20.6) remained associated with hepatitis C infection.
”Despite having more than 575 person-years of observation in this sexually active sample and documented new sexually transmitted viral infections like HSV-2 and HIV, no cases of HCV antibody seroconversion were detected? note the investigators. They add, “In addition, no correlation was found between HCV antibody prevalence and recent sexual behaviors such as number of sexual partners in the past year or unprotected insertive or receptive anal sex…HCV is inefficiently spread through sexual contact." They conclude that hepatitis C prevention efforts should focus on injecting drug users, “as the sexual transmission of hepatitis C continues to appear uncommon."
Further information on this website
Hepatitis C - overview
Hepatitis C - factsheet
Barebacking the sole common risk factor in London's sexually transmitted hepatitis C epidemic - news story
Sexual transmission of HCV: the debate continues - news story
Sexual transmission of HCV not seen in US women’s HIV cohort - news story
Hammer GP et al. Low incidence and prevalence of hepatitis C virus infection among sexually active non-intravenous drug-using adults, San Francisco, 1997 - 2000. Sexually Transmitted Diseases 30: 919 - 924, 2004.