Hepatitis C virus (HCV) was first identified in 1989 as the principal cause of posttransfusion non-A non-B hepatitis [1]. Worldwide an estimated 170 million people are infected with HCV; due to shared routes of transmission, 4-5 million are coinfected with HIV [2]. HCV is usually transmitted parenterally. Within high-income countries, HCV transmission through blood products has effectively been halted, leaving injecting drug use (IDU) as the major cause of new HCV infections [3]. In medium and low-income countries, however, iatrogenic HCV transmission still accounts for a significant proportion of incident infections [4].
Permucosal sexual transmission of HCV remains controversial. Differences in sexual orientation and risk behaviour of the study population; study design; the presence of unmeasured parental routes of HCV transmission; and the use of molecular epidemiological techniques to confirm transmission between partners, might explain conflicting results [5]. Anti-HCV prevalence rates up to 28% have been reported among spouses of HCV-infected individuals, increasing with relationship duration [6-8]. However, sexual transmission has often been ruled out using molecular typing [9-11]. Even when molecular typing confirmed a common source of infection, other possible routes of transmission within the household could not be excluded [12]. Based on prospective cohort studies, sexual transmission of HCV is relatively rare in monogamous heterosexual relationships and varies from 0 to 0.6% per year [13-16]. A slightly higher risk, 0.4-1.8% per year, has been reported for heterosexuals with multiple partners or those at risk for sexually transmitted infections (STIs) [5].
Since 2000 outbreaks of acute HCV among HIV-positive men who have sex with men (MSM) who denied IDU have been reported from Europe [17-22], the United States [23-25] and Australia [26]. Remarkably, the majority of HCV infections were related to permucosal rather than parenteral risk factors, reopening the discussion on the importance of sexual transmission. This review will synthesize the most recent epidemiological, immunological and management issues that have emerged as a result of the epidemic of acute HCV among HIV-infected MSM. Studies were identified by MEDLINE using appropriate keywords and supplemented with perusal of reference lists of relevant publications and abstracts of recent relevant conferences.
Epidemiology of hepatitis C virus in men who have sex with men
Hepatitis C virus prevalence
In early cross-sectional studies, anti-HCV prevalence among MSM ranged from 0 up to 23%, which was higher than that observed among voluntary blood donors and heterosexuals at risk for STI (reviewed in [3], [27-29]). However, many of these studies did not incorporate information on IDU. The studies that did, revealed an anti-HCV prevalence of 1-7% among MSM who denied IDU versus 25-50% among MSM with a history of IDU [20,30-32]. HCV prevalence was also consistently higher in HIV-positive MSM (3-39%) than MSM without HIV (0-19%) [20,30,31,33-35]. It was concluded that IDU was responsible for the majority of HCV infections in MSM and that HIV might play a role in HCV transmission.
Recent outbreaks of HCV among HIV-positive MSM who denied IDU in Europe, USA and Australia suggest sexual transmission of HCV [17-24,26]. A study from the UK showed that acquisition of HCV in MSM with primary HIV infection increased from 0% in 1999 to 4% in 2006 [36]. In the Netherlands, a bi-annual cross-sectional survey among STI-clinic attendees showed an alarming increase in HCV prevalence among HIV-infected MSM from 15% in 2007 to 21% in 2008, compared to an estimated HCV prevalence of 1-4% before 2000 [37]. Only 5% of HIV-positive MSM reported IDU, and a relatively high proportion was diagnosed with acute HCV infection. In contrast, a large study among 2268 HIV-infected MSM in Europe who were recruited between 1995 and 2003 showed a HCV prevalence of 6.6% [38], which is in line with the HCV prevalence observed at the beginning of the HIV epidemic. The HCV prevalence among HIV-negative MSM who deny IDU is low and comparable to that of the general population [37,39-41].
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