Incidence of hepatitis C virus infections has increased eighteen fold in HIV-positive gay men in Switzerland since 1998, investigators report in the online edition of Clinical Infectious Diseases. Half of all infections in gay men occurred between 2008 and 2011. In contrast, incidence of hepatitis C fell in HIV-positive injecting drug users and remained stable in HIV-positive heterosexuals.
“We found that the yearly incidence rate had decreased in IDU [injecting drug users], remained stable in HET [heterosexuals] and dramatically increased in MSM [men who have sex with men],” write the authors. “In MSM, a history of inconsistent condom use and a past episode of syphilis were significantly associated with HCV [hepatitis C virus] seroconversion.”
Liver disease caused by hepatitis C is now a major cause of serious illness and death in people with HIV. For many years, hepatitis C co-infection almost exclusively occurred in injecting drug users and recipients of blood products.
However, over the past decade there have been outbreaks of sexually transmitted hepatitis C in HIV-positive gay men. These infections have been linked to unprotected sex, traumatic mucosal activities such as fisting, and have also occurred within sexual networks. Such an outbreak has been observed among HIV-positive gay men in Zurich.
Investigators from the Swiss HIV Cohort Study wished to establish a better understanding of the wider dynamics of hepatitis C epidemiology in the HIV-positive people in their care.
They therefore examined incidence of the infection in three risk groups: gay men, injecting drug users and heterosexuals.
Incidence rates were monitored over a 13-year period, between 1998 and 2011.
The investigators also examined whether any risk factors for incident hepatitis C infections in gay men could be identified.
A total of 12,000 people were included in the study. Prevalence of hepatitis C co-infection at baseline was 3% for gay men, 92% for injecting drug users and 11% for heterosexuals.
A total of 3333 gay men were then included in the prospective analysis, as were 123 injecting drug users and 3078 heterosexuals.
During follow-up, 3% of gay men became infected with hepatitis C, as did a third of injecting drug users and 1% of heterosexuals.
The dynamics of the hepatitis C epidemic differed between risk groups.
In gay men, incidence increased from 0.23 per 100 person years in 1998 to 4.09 per 100 person years in 2011. In all, 51 of the 101 infections observed over the entire study period occurred between 2008 and 2011.
“Clinicians and patients should be aware of the risk of acute HCV infections in MSM,” write the researchers. “Intensified prevention and counselling should be performed.”
In contrast, incidence among injecting drug users declined from 13.89 per 100 person years in 1998 to 2.24 per 100 person years in 2011. Only three infections in this group were recorded between 2008 and 2011.
“Switzerland’s long-term heroin prescription programme likely contributed to the decreasing incidence of HCV seroconversion in this population,” comment the investigators.
Incidence in heterosexuals was low at approximately 0.5 per 100 person years across the study period. The investigators speculate that many of these infections may in fact be due to either undisclosed injecting drug use or due to sex between men. “Recent phylogenetic studies within the Swiss HIV Cohort Study…revealed that approximately 11% of HIV-pol sequences from heterosexuals were linked to transmission clusters in MSM,” note the authors.
Risky sexual behaviour appeared to be the driving the epidemic in gay men.
The investigators found that inconsistent condom use doubled the risk of hepatitis C seroconversion (aHR = 2.09; 95% CI, 1.33-3.29) in this group. Incident hepatitis C infection was also associated with a previous syphilis diagnosis (aHR = 2.01; 95% CI, 1.39-3.20).
Two-thirds of hepatitis C infections among gay men involved hepatitis C genotype-1 and 19% genotype-4. These are the harder to treat of the hepatitis C genotypes.
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