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Hepatitis C virus infection is rising among gay and bisexual men in San Diego
Liz Highleyman, 2016-12-05 07:20:00

The prevalence of hepatitis C virus (HCV) infection among HIV-positive men who have sex with men in San Diego has increased over the past 15 years, especially among men who do not inject drugs but use methamphetamine, according to a study presented at the 2016 AASLD Liver Meeting this month in Boston. Another study by the same researchers found that post-treatment reinfection is also a concern in this population.

Starting in the early 2000s researchers in the UK and elsewhere in Europe began reporting clusters of apparently sexually transmitted acute HCV infection among HIV-positive gay and bisexual men in large cities; similar outbreaks followed in cities in Australia and the US. A number of risk factors have been implicated – including condomless anal sex, fisting, group sex, other sexually transmitted infections and non-injection drug use – but these have not been consistent across studies. HCV sexual transmission remains rare among HIV-negative men who have sex with men.

Antoine Chaillon of the University of California at San Diego and colleagues assessed the incidence of HCV infection among men who have sex with men in San Diego. To date, most reports on HCV sexual transmission among gay men in the US have come from New York City and San Francisco.

The researchers did a retrospective cohort analysis of HCV incidence among HIV-positive men who have sex with men attending the UCSD Owen Clinic, the largest HIV clinic in San Diego, between 2000 and 2015.

The analysis included 2396 clinic clients who had a negative HCV antibody test at baseline. The median age was 38 years, 68% were white and 10% were black. Only 7% reported having ever injected drugs, but 59% said they had ever used methamphetamine.

Incident or new infection was defined as a positive HCV antibody or HCV RNA test following a negative test. Participants were tested for HCV a median of three times with a median interval of 1.2 years between tests.

A total of 149 HCV seroconversions occurred during 12,560 person-years of follow-up time, yielding an incidence rate of 1.19 per 100 person-years (95% CI 1.01-1.39). New HCV cases were identified an average of 10.6 years after HIV diagnosis and 3.6 years after the first negative HCV test.

Men with new HCV infection did not differ from the cohort as a whole in terms of age or race/ethnicity. However, the newly infected men were significantly more likely than uninfected men to have injected drugs (18 vs 7%) and used methamphetamine (82 vs 58%).

HCV incidence was significantly higher among men who reported injection drug use compared to those who did not (2.6 vs 0.97 per 100 person-years). Likewise, HCV infection was significantly more common among men who said they used methamphetamine compared to those who did not (1.53 vs 0.52 per 100 person-years).

Overall HCV incidence increased over time, from just 0.36 new infections per 100 person-years between 2000 and 2003, to 1.52 per 100 person-years between 2012 and 2015. New HCV cases among men who did not inject drugs or use methamphetamine rose slowly, while incidence among men who did use methamphetamine rose steeply over time. Incidence among men who injected drugs rose sharply from 2000-2003 to 2004-2007, but then stabilised and declined between 2008-2011 and 2012-2015 – perhaps reflecting an increase in harm reduction practices.

"These findings suggest that HCV incidence is increasing among HIV+ MSM in San Diego," the researchers concluded. "These rates are similar to London and other major European cities, and double that observed in the US Multicenter AIDS Cohort Study."

"This study also documented HCV infection among HIV+ MSM who do not inject drugs and an increased HCV incidence among individuals reporting methamphetamine use," they added. "Further work determining the epidemic trajectory and prevention required to control the epidemic is needed.