Evidence was been published by Australian investigators in the October edition of AIDS demonstrating the sexual transmission of hepatitis C virus (HCV) amongst HIV-positive gay men.
The sexual transmission of hepatitis C has been well-described amongst HIV-positive gay men in England, the Netherlands, France and Germany, and the Australian investigators believe that their evidence shows that “factors driving the epidemiology of acute HCV infection in this population are prevalent globally.”
The Australian Trial of Acute Hepatitis C (ATAHC) is a prospective study of the natural history and treatment outcome of acute hepatitis C. It is being conducted at 21 sites across Australia.
Recruitment started in 2004 and the investigators reported on 120 cases. Detailed questionnaires enquiring about the patients’ risk behaviour are completed on entry to the study and then at six-monthly intervals. Both the patients and their treating physicians were asked to assess the likely mode of hepatitis C transmission.
A marked difference in the likely mode of hepatitis C transmission was observed in HIV-positive (26) patients and HIV-negative (94) individuals.
All the HIV-positive individuals were gay men or men with a history of sex with another man, and 50% identified sex with another man as their most likely mode of hepatitis C infection. Furthermore, of these 13 men, four said that they had a sexual partner who was infected with hepatitis C.
By contrast, only 6% of the HIV-negative individuals said that sex was their likely mode of hepatitis C acquisition and only one said that sex with another man was his likely risk behaviour.
Even when injecting drug use was reported by HIV-positive men, there were important differences with the injecting behaviours of HIV-negative individuals, with the HIV-positive men reporting a significantly older age at initiation of injecting drug use (30 vs. 23 years, p = 0.005), and the injection of methamphetamine rather than heroin.
“The potential mechanisms for increased rates of sexual transmission of HCV in the HIV-positive population may involve higher serum and semen viral loads, immunological impairment in the mucosal compartment, or unique high-risk sexual behaviours”, write the investigators. They add, “comprehensive analysis of virological and behavioural risk factors in both HIV-positive and HIV-negative individuals will help further define the mechanisms underlying permucosal HCV transmission in HIV-positive men who have sex with men.”
Matthews GV et al. Further evidence of HCV sexual transmission among HIV-positive men who have sex with men: response to Danta et al. AIDS 45: 2112 – 2113, 2007.