Sexual transmission of hepatitis C virus (HCV) is taking place in HIV-negative as well as HIV-positive gay men, according to data from Brighton – the United Kingdom’s city of highest HIV prevalence – presented on Wednesday to the Fourteenth Conference on Retroviruses and Opportunistic Infections in Los Angeles.
In recent years there have been a number of studies reporting sexual transmission of HCV, primarily in HIV-positive gay men in western Europe. First observed in 2002in the UK, similar outbreaks have also been reported in the Netherlands, Switzerland and France.
Outbreaks of acute HCV infection amongst HIV-positive gay men (and other men who have sex with men [MSM] who may not identify as gay or bisexual) have been detected because HIV-positive people routinely undergo HCV antibody screening as well as regular liver function tests in order to monitor antiretroviral toxicity. However, HIV-negative gay men do not routinely receive such testing, so evidence of a possible parallel sexually transmitted HCV epidemic in this population has not been reported until now. Nevertheless, even the earliest reports from the UK included a small number of HIV-negative men.
Researchers from Royal Sussex County Hospital undertook a study to explore sexual transmission of HCV among HIV-positive and HIV-negative men attending Brighton’s main sexual health and HIV clinic between 2000 and 2006. Due to the high local HCV infection rate in this population, all MSM attending the clinic have been screened for HCV since 2000. Men were included in the analysis if they had one documented negative HCV antibody test and subsequently tested HCV antibody positive. Participants without a documented HIV antibody test results were classified as HIV status unknown. Men who reported injection drug use were excluded.
Out of a total of 7,169 clinic patients, 3,907 had at least one HCV antibody test, and 25 were newly diagnosed with HCV. Amongst this group, 16 were HIV-positive, five were HIV-negative, and four had an unknown HIV status.
HCV incidence increased from zero in 2002 to 1.4 per 1,000 patient years in 2003. Incidence increased in 2004 and 2005 to 1.6 and 1.9 per 1,000 patient years, respectively, and then jumped to 3.6 per 1,000 patient years in 2006.
HIV-positive men were found to be about thirteen times more likely to have a new HCV diagnosis compared with HIV-negative men. Dr Daniel Richardson, presenting, described the difference as “dramatic,” though the differences did not attain statistical significance due to the small numbers.
HCV incidence rates in HIV-negative men and those of unknown HIV status were similar.
In accordance with previous reports, incident HCV diagnosis was associated with fisting, unprotected anal intercourse, multiple sex partners, and infection with other sexually transmitted infections.
The researchers concluded there has been a significant increase in new HCV diagnoses amongst gay men attending their clinic, and – contrary to previous reports – these have not been seen exclusively in HIV-positive men. While HIV-positive serostatus remained a major risk factor for HCV infection, a substantial number of new infections occurred in HIV-negative men or those with unknown HIV serostatus.
Importantly, all but one of the nine men who were HIV-negative or had unknown HIV status at the time of their HCV diagnosis later went on to become infected with HIV, suggesting that they continued to engage in risky behaviour. Dr Richardson recommended that this high-risk group should be especially targeted for HIV prevention efforts. He also suggested that routine HCV antibody testing should be considered for all MSM, regardless of HIV serostatus.