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]
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
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
During follow-up, 3% of gay men became
infected with hepatitis C, as did a third of injecting drug users and 1% of
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
“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.
“It is crucial that HIV-infected MSM are
counseled with regard to the risk of sexual activities that involve traumatic
mucosal sex, and that condoms are consistently used in sexual risk situations,”
conclude the investigators. “The example of IDUs demonstrates that it is
possible to reduce the incidence of HCV infections through improved screening
and preventative interventions.”