The hepatitis C epidemic in HIV-positive gay men is being
driven by both sexual transmission and injecting drug use, Australian research
published in the online edition of Clinical
Infectious Diseases suggests. Sexual risk and injecting drug use were reported
by HIV-positive gay men newly diagnosed with the virus.
Phylogenetic analysis showed that 51% of infections in gay
men could be placed within transmission clusters. No heterosexual injecting
drug users were identified in the transmission clusters that involved gay men,
suggesting to the investigators that “these networks of HCV [hepatitis C virus
transmission] are predominately defined by sexual orientation rather than risk
There were few cases of sexual transmission of hepatitis C
in HIV-negative individuals, and in every instance the individual had a partner
who was known to be infected with hepatitis C.
Separate US research conducted at HIV treatment centres
across the country showed that there is a low incidence of hepatitis C in
HIV-positive men. However, 75% of all new diagnoses appeared to be related to
sexual risk factors rather than injecting drug use.
Acute hepatitis C in
Investigators from the Australia Trial of Acute Hepatitis C
(ATAHC) wished to establish if the epidemics of hepatitis C in injecting users
and HIV-positive gay men overlapped. They also wished to see if there was any
evidence of sexual transmission of the virus in HIV-negative individuals.
A total of 163 patients who had recently been infected with
hepatitis C were recruited to the study, 29% of whom were HIV-positive.
Injecting drug use was identified as the route of hepatitis
C transmission in 73% of patients, sexual transmission in 18%, and other (such
as medical transmission or assault), in 9% of cases.
Of the 29 cases of sexual transmission, four involved women
who had a male partner who was known to be hepatitis C-infected.
Only two of the men who acquired hepatitis C sexually were
HIV-negative. One believed he was infected by a woman, and the other reported
sex with another man.
All 23 HIV-infected individuals who acquired hepatitis C
were gay men.
The investigators constructed a phylogenetic tree using
samples taken from 112 patients. This enabled them to identify four distinct
transmission clusters. Only 8% of HIV-negative individuals could be placed
within a transmission network. This involved a pair of female HIV-negative
injecting drug users.
However, 51% of infections in gay men could be placed in
The only HIV-negative gay men who was infected with
hepatitis C was in a cluster with two HIV-positive gay men who injected drugs.
“These findings further extend the debate on the role of
sexual and IDU-related transmission of HCV in HIV-infected and HIV-uninfected
MSM populations and have implications for appropriate targeting of future
public health messages,” comment the investigators.
Incident hepatitis C
among HIV-positive men in the US
In a separate study US investigators examined rates of
incident hepatitis C infections among HIV-positive men between 1996 and 2008.
Earlier studies have shown have identified outbreaks of
sexually transmitted hepatitis C in New York and California. The researchers
wished to see if there was evidence of an epidemic elsewhere in the US.
A total of 1830 men who were clear of hepatitis C at baseline
and who had at least one subsequent antibody test were included in the study.
At the time of the first test 94% of individuals were taking HIV therapy, and
only 6% reported current or prior injecting drug use.
There were 36 hepatitis C infections, and this provided an
incidence of 0.51 cases per 100 person years. Only 25% of individuals newly
infected with hepatitis C had any history of injecting drug use. The
investigators believe that sexual transmission is the most likely explanation
for the other infections.
“At-risk HIV-infected persons should have access to ongoing
HCV surveillance,” conclude the investigators.