Injecting drug use is the behaviour most associated with hepatitis C virus infection in both HIV-positive and HIV-negative gay men in Sydney, a study published in the online edition of Sexually Transmitted Infections shows.
The Australian researchers also found that rates of hepatitis C infection were about ten times higher in HIV-positive men than they were in HIV-negative men.
Although no new hepatitis C infections were detected in men with HIV, there were five in the HIV-negative men, and the investigators found that many of these men had reported sex with an HIV-positive man, use of sex toys, fisting, and ulcerative sexually transmitted infections.
Hepatitis C is a blood-borne virus and its main mode of transmission is injecting drug use. Sexual transmission of the virus is thought to be rare. However there have recently been outbreaks of hepatitis C amongst HIV-positive gay men and sex seems to be the most likely mode of transmission.
It seems that sexual activity that involves contact with blood is associated with the transmission of hepatitis C in HIV-positive gay men, for example fisting, use of sex toys, and unprotected anal sex, especially in the context of recreational drug use and group sex.
Investigators in Sydney, Australia wished to obtain a better understanding of the transmission of hepatitis C in gay men.
They therefore analysed the results of two studies – one involving HIV-negative men, the other men with HIV – to determine the prevalence, incidence, and risk factors for hepatitis C.
Study populations
A total of 1427 HIV-negative men recruited to the Health in Men (HIM) study and 245 HIV-positive men from the Positive Health study were included in the investigators’ analyses.
Information from the HIM study from 2001 to 2007 was studied, with the Positive Health study providing testing data from 2005 to 2007.
Both these studies were therefore able to analyse the results of tests for hepatitis C conducted since the sexual transmission of the epidemic became apparent in HIV-positive gay men in Europe in around 2002.
Injecting drug use strongly associated with hepatitis C in HIV-negative men
At baseline, 15 HIV-negative men were infected with hepatitis C. This provided a prevalence of approximately 1%. The investigators note that this prevalence is comparable to that in the general Australian population.
Injecting drug use was strongly associated with infection with hepatitis C (OR = 56.18; 95% CI 12.55-251.5). Only two of the hepatitis C-infected men did not report this behaviour, and the investigators note that these men both had tattoos or piercings, a possible mode of hepatitis C transmission.
Other characteristics associated with an increased risk of hepatitis C infection on entry to the study were older age, number of sexual partners, initiating anal sex at a younger age, and a history of sex work.
There were five new infections with hepatitis C during the study, providing an incidence rate of 0.11 per 100 person years.
Only one of the men newly infected with hepatitis C reported injecting drug use. Four of the men (including the individual with a history of injecting drugs) said that they had sex with an HIV-positive man prior to their infection with hepatitis C.
As regards other sexual risk factors, unprotected anal sex was reported by one man, three said that they had used sex toys, and one reported fisting. Syphilis and infection with genital herpes were each reported by one individual.
High hepatitis C prevalence in HIV-positive gay men
Hepatitis C prevalence was much higher in the HIV-positive cohort. At baseline, 23 individuals were co-infected, providing a prevalence of 9.39%. Questions about injecting drug use were answered by 18 men, and 16 said that they had a history of such behaviour.
Despite the contemporary epidemic of sexually transmitted hepatitis C amongst HIV-positive gay men in northern Europe, there were no new infections with this virus during follow-up in this cohort.
The investigators note that HIV-positive gay men have historically had a higher prevalence of hepatitis C virus than their HIV-negative peers. For example, in a 1980s Sydney clinic cohort, 12% of those with HIV were infected with hepatitis C compared to 4% of HIV-negative men.
Although low, the incidence of what seems to be sexually acquired hepatitis C in HIV-negative gay men was higher in Sydney than has been reported in a number of other recent studies.
The low numbers of infections made statistical analysis difficult. There was only a weak association with unprotected anal sex with an HIV-positive man. However, the investigators noted that two of the recently infected men reporting sex with an HIV-infected man were diagnosed with syphilis or genital herpes. They therefore suggest “as both…are ulcerative sexually transmitted infections, these data suggest that the presence of ulcers may have facilitated hepatitis C transmission.”
“In these highly sexually active cohorts of homosexual men prevalent hepatitis C infection was almost ten times more common in HIV-positive men, and was related to injecting drug use in about 90% of cases in both HIV-negative and HIV-positive men”, comment the investigators.
Sexual risk factors seemed to be involved in the few new infections they identified, and the investigators conclude, “more carefully designed studies are warranted to elucidate whether the increase in the hepatitis C epidemic in homosexual men in some settings is attributable to sexual transmission or to increases in other risky behaviours, such as injecting drug use, and body piercing and tattooing.”
Jin F et al. Prevalence, incidence and risk factors for hepatitis C in homosexual men: data from two cohorts of HIV negative and HIV positive men in Sydney, Australia. Sex Transm Infect (online edition), 2009.