Hepatitis C infection amongst HIV-positive gay men attending an STI clinic in Amsterdam continues to be extremely common, the Eighteenth International AIDS Conference in Vienna heard. But the growing epidemic of co-infection appears to have stopped, with no new, acute hepatitis C infections being detected since the second half of 2008, and researchers are not sure why.
Anouk Urbanus of the Amsterdam Public Health Service has published a series of twice-yearly surveys of HIV and hepatitis C infection at the Amsterdam clinic; see aidsmap report: Hepatitis C spreading rapidly amongst HIV-positive gay men in Amsterdam for a report on the previous survey. During the series of surveys, data were collected on 5177 clinic attendees, of whom 1282 were gay men, though only about 300 to 400 gay men and 90 to 150 HIV-positive gay men were surveyed during any one six-month interval.
The previous surveys were alarming, as they appeared to document a rapidly increasing hepatitis C epidemic. Between January 2007 and January 2008 hepatitis C prevalence among HIV-positive gay men attending the clinic grew by 50%, from 13.3% to 21%. More worryingly still, the proportion of co-infected men who were detected with acute hepatitis C infection – within the first three months – grew from 11% of all co-infected men to 38% within six months, indicating not just a growing, but an accelerating, epidemic.
However, prevalence fell back to 16% in the second half of 2008 – and, averaged over one year rather than six months, prevalence has remained at 14.7% since.
More strikingly, not a single new, acute case of hepatitis C has been seen since January 2008, though chronic cases may continue to be picked up amongst new clinic attendees.
In terms of causes of infection, fisting, use of GHB and having HIV were the strongest predictors of hepatitis C, though fisting was so strongly associated with other high risk sexual behaviour like sex toys and group sex, it is perhaps better to speak of a cluster of sexually risky behaviours rather than single one out.
There were five cases of hepatitis C reported amongst HIV-negative gay men, a prevalence of 1.7%. Three of these five cases reported injecting drugs.
Phylogenetic analysis showed that the majority of cases amongst HIV-positive men, and all of the acute cases, occurred in four closely related clusters containing seven to twelve men each, and appeared to show rapid-fire transmission between men attending group sex events, or at least closely sexually connected. Another ‘cluster’ was a pair of infections, one of whom was HIV-negative, that might indicate a sexual or needle-sharing event. Three of the other four HIV-negative infections were related to each other in a looser cluster, suggesting less coincidence in time.
Presenter Anouk Urbanus said she could not speculate on the reasons why ongoing transmission of hepatitis C in Amsterdam appeared to have abruptly stopped.
Urbanus AT Continuing increase in hepatitis C virus infections among HIV-infected men who have sex with men (MSM)? Eighteenth International AIDS Conference, Vienna, abstract WEPDC104, 2010.
