Hepatitis C: A Risk for Gay Men
April 14, 2015
Over a decade ago, doctors in Europe began reporting clusters of new hepatitis C infections among HIV-positive gay and bisexual men. Given their lack of other risk factors, the culprit appeared to be sexual transmission. This was greeted with surprise and skepticism, as it was assumed that sexual transmission of hepatitis C virus (HCV) was rare. But today there is a growing consensus that sex is a leading cause of new HCV infections among men who have sex with men (MSM), especially those who have HIV.
"Among gay men, I think the vast majority who acquired HCV in the past decade have gotten it from sex," says Daniel Fierer from Mount Sinai Medical Center in New York City.
HCV is a blood-borne virus that had been most often transmitted by sharing needles or by blood transfusions (before blood was tested for the virus). The CDC lists sex as an "inefficient means" of HCV transmission. Public health messages have said that the risk of sexual transmission is very low and that people with HCV do not need to change their sexual practices. This advice was based on studies showing that transmission is rare in monogamous heterosexual couples, ranging from 0% to about 3%.
But these findings don't hold for other groups. Other studies have shown that both heterosexual and gay people with multiple sex partners, HCV-positive partners, or partners who inject drugs have a higher chance of getting hepatitis C.
HCV and HIV
Because the transmission routes are similar, about a third of people with HIV also have HCV, and many people who got HIV through injection drug use also have HCV. But among gay and bisexual men with HIV, sex appears to be increasingly common as a means of HCV transmission.
"For gay men who don't inject drugs but have a lot of sex, if they get HCV, they're likely to have gotten it through sex," says Brad Hare, Director of HIV Care and Prevention at Kaiser Permanente in San Francisco.
In 2002 researchers reported several cases of new HCV infections among HIV-positive gay men at sexual health clinics in London. Within a year, the number of new cases approached 50. Before long, similar clusters were reported in France, Germany, the Netherlands, and Switzerland. These were followed a couple of years later by reports from Australia, the U.S., and Japan.
New HCV infections in gay men with HIV began to climb steeply around 2005. Investigators from Amsterdam's public health service have traced HCV prevalence, or total cases, among HIV-positive gay men over two decades. The proportion of these men testing positive for HCV antibodies rose from 6% in 1995 to a peak of 21% in 2008, with nearly one third having a new infection. The number then appeared to level off, which the researchers said could be due to greater awareness and prevention, or just that the pool of susceptible men was "saturated".
Similar reports emerged a bit later in the U.S. In 2006 Annie Luetkemeyer reported nine cases of new HCV among men with HIV seen at San Francisco General Hospital, with a majority reporting only sexual risk factors. The next year, Fierer first reported on a group of HIV-positive gay men in New York with new HCV infections despite no traditional, non-sexual, risk factors. Disturbingly, some of them had unusually rapid liver fibrosis. And in 2009, Lynn Taylor reported that 75% of new HCV infections among HIV-positive gay and bisexual men in several AIDS Clinical Trials Group studies were likely due to sexual transmission.
Genetic studies have shown that HCV strains from MSM closely follow sexual networks within and even across cities. Several HIV-positive gay men in European cities, for example, were infected with HCV genotype 4, a Middle Eastern strain that is otherwise uncommon in Europe. Notably, the HCV strains circulating among gay men are usually not closely related to the strains circulating among people who inject drugs in the same city.
By now the risk of HCV sexual transmission among HIV-positive gay and bisexual men is widely recognized. But what about their HIV-negative counterparts?
Since the topic first hit the radar a decade ago, researchers have seen few cases of apparently sexually transmitted HCV in HIV-negative men. But some experts have suggested that sexual transmission of HCV among HIV-negative men is found less often only because we don't look for it. HIV-negative people are seldom tested for HCV and don't usually have regular liver function tests. But the few studies that have specifically looked for HCV in HIV-negative gay men have found infection rates similar to those of the general population.
After clinicians in Brighton, England, observed a high rate of new HCV infections among men with HIV at their sexual health clinic, they decided to test all clients, regardless of HIV status, starting in 2000. While several cases of HCV were detected among HIV-negative men, they were 13 times less likely to get it than HIV-positive men.
In Amsterdam, while HCV prevalence among men with HIV rose from 6% to 21% between 1995 and 2008, cases in HIV-negative men stayed low and stable at around 0.5%. Other studies in Sweden, Switzerland, and the U.K. have seen HCV prevalence rates among HIV-negative gay men ranging from 0.2% to 0.7% -- similar to the general population of those countries.
At last year's ICAAC meeting, Katie McFaul from Chelsea and Westminster Hospital reported finding 44 HIV-negative gay men with new HCV at three sexual health clinics in London, out of about 34,000 clients tested for the virus (a rate of less than 1%). At the same conference, Swiss researchers reported that only one out of 654 mostly HIV-negative gay men tested at their clinic had HCV. His only risk was condomless anal sex.
What Are the Risk Factors?
A wide range of risk factors have been linked to HCV among MSM, including anal sex, fisting, rimming, multiple sex partners, group sex, sex at sex clubs or bathhouses, use of noninjected recreational drugs, sex while using drugs, and having other sexually transmitted diseases (STDs). Injection drug use does not appear to play much of a role.
The strongest predictor of HCV among gay men is anal sex, especially receptive sex without a condom. In some studies, every man with new HCV reported being an anal sex bottom.
This raises the question of whether HCV is sexually transmitted mainly through blood or through semen. HCV is known to spread most easily through direct contact with infected blood. Some experts, therefore, have concluded that HCV transmission is probably due to exposure to blood during sex.
Some sex activities like piercing and whipping can cause bleeding, and one recent study from Amsterdam found that gay men in the leather, rubber, or denim scenes have higher HCV rates. But sex doesn't have to be "rough" to be risky. Anal intercourse can cause small tears in the rectal lining that could increase the likelihood of infection.
"Researchers talk about traumatic sex, but that's an unfair thing to say about gay men," says Fierer. "Do they mean all anal intercourse is traumatic? People don't identify their anal sex as traumatic."
Even hangnails or minor cuts on the hands, genitals, or elsewhere could provide a portal for viral entry or exit. The amount of blood doesn't have to be large or even visible to allow for HCV transmission. "It doesn't have to be some blood-letting exercise," Fierer stresses. Being fisted, using sex toys, or bottoming with multiple partners can injure the rectal lining, providing easier access for the virus. During group sex, HCV in blood or semen may be transferred from one person to the next on penises, fists, or toys.
Non-injection drug use may play a role if people share straws or rolled bills for snorting drugs or pipes for smoking, since small amounts of blood may be left on the equipment. Some drugs enable prolonged sex, while others can dry out mucous membranes or cause numbness that allows more vigorous penetration.
Other STDs, including syphilis and genital herpes, cause sores or ulcers that make it easier for HCV to get in and out of the body. Anal warts caused by HPV may also add to the risk. Other infections like gonorrhea and chlamydia cause inflammation that may aid HCV transmission.
It's difficult to tease out the specific contributions of various risk factors because multiple activities often occur together and most gay men do not have only one kind of sex. If an HIV-positive man with undiagnosed chlamydia takes ecstasy and goes to a sex club where he fists one partner, is penetrated with a previously used sex toy, and then bottoms for anal sex, it's hard to tell which of these factors is to blame if he gets HCV.
But none of this explains why receptive anal sex is such a major risk factor. "Where is the HCV coming from?" Fierer asks. "I think it's coming from semen -- that's the simplest explanation, since penises don't bleed."
Several studies have detected HCV in semen, though usually at low levels and not all the time. One Australian study, for example, found that 44% of men with HCV had detectable virus in their semen at the start and 74% did at least once during follow-up. Other research has shown that men with HIV have higher HCV viral loads and are more likely to have HCV in their semen than HIV-negative men. Furthermore, men with new HCV infection have more HCV in their semen than those with chronic infection.
"Hepatitis C is more efficiently transmitted through blood and less through sex, so if a gay man has both types of exposure, it's probably blood that's causing it," Hare summarizes. "In the absence of blood, semen is a less efficient but possible route of HCV infection."
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