Australian
Researchers Provide Further Evidence of Sexual Transmission of HCV among HIV Positive
Gay Men By
Liz Highleyman
Since
the early 2000s, doctors in the U.K. and elsewhere in Europe have reported outbreaks
of apparently sexually transmitted acute hepatitis
C virus (HCV) infection among mostly HIV
positive men who have sex with men (MSM). At
the 4th International AIDS Society Conference
on HIV Pathogenesis, Treatment, and Prevention this past July, researchers
presented an analysis of 190 such cases in the U.K., Netherlands, Germany, and
France, showing
how the HCV strains of these patients are related.*
In a letter in
the October 1, 2007 issue of AIDS, Gail Matthews and colleagues presented
information about a similar small outbreak of apparently sexually transmitted
HCV among MSM in Australia. The
Australian Trial in Acute Hepatitis C (ATAHC) is a prospective study of the natural
history and treatment outcomes of patients with acute HCV infection at 21 sites
in Australia. A total of 120 participants have enrolled since August 2004. At
baseline and every 6 months, subjects completed detailed risk behavior questionnaires.
The cohort population
includes a high proportion of injection drug users, and HCV acquisition through
injection drug use was assumed if either the patient or a clinician identified
injecting as the most likely transmission route. An
interim data analysis identified significant differences in the most likely risk
factors for HCV acquisition between the 26 HIV positive and 94 HIV negative participants
studied to date. While
80% of the HIV negative subjects had injection drug use as their most likely risk
factor, this dropped to 46% among the HIV positive individuals. Conversely, 50%
of the HIV positive subjects, but only 1% of the HIV negative group, had male-to-male
sexual contact as their primary identified risk factor. Heterosexual sex was rarely
a risk factor (5% in the HIV negative group, 0% in the HIV positive group). More
HIV negative people had a risk factor other than injection drug use or sex (14%
vs 4%). All 26
HIV positive participants gave a history of male-to-male sex, and sexual contact
with a male partner was identified as the most likely mode of HCV acquisition
for 13. Of these 13, 38% reported that their most likely mode of transmission
was having a sexual partner known to have chronic hepatitis C, while the others
reported sex with same-sex partners of unknown HCV status. In
contrast, sexual transmission was identified as the most likely mode of HCV transmission
for only 6% of the HIV negative group (5% heterosexual and 1% male-to-male). Further,
the HIV positive participants who report injecting drugs differed from the HIV
negative injectors, in that they started injection at a later age (30 vs 23 years)
and more often preferred crystal methamphetamine as opposed to heroin as their
drug of choice. "Our
findings are of interest for a number of reasons," the researchers wrote.
"The apparent high rate of non-injecting sexual HCV transmission within HIV-positive
MSM seen in this multicentre Australian study mirrors that described in Europe,
and suggests that factors driving the epidemiology of acute HCV infection in this
population are prevalent globally." They
added that their study, unlike the European cohorts, has concurrently enrolled
both HIV positive and HIV negative individuals, "thus allowing a unique comparison
of the differences between these two groups in terms of behavioural, immunological
and virological characteristics of acute hepatitis C." Although
sexual transmission of HCV among HIV negative MSM appears uncommon, it does sometimes
occur, according to a study of men in Brighton, U.K., presented at the 14th
Conference on Retroviruses and Opportunistic Infections this past February. 10/02/07 Reference
GV
Matthews, M Hellard, J Kaldor, and others. Further evidence of HCV sexual transmission
among HIV-positive men who have sex with men: response to Danta et al [Correspondence].
AIDS 21(15): 2112-2113. October 1, 2007.
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