There is an emerging epidemic of sexually transmitted hepatitis C virus (HCV) among HIV-positive men who have sex with men (MSM), with men who are then cured of hep C at very high risk of being reinfected with that virus. Men who have receptive anal intercourse without a condom and who have sex while high on drugs are at greater risk.

Publishing their findings in the journal AIDS, researchers conducted a meta-analysis of 15 studies of more than 13,000 HIV-positive MSM who did not use injection drugs.

The rate of hep C acquisition among injection drug users (IDUs) is about 10 to 40 percent per year. By comparison, the acquisition rate among MSM is small, but not insignificant, and it is on the rise.

During 93,100 person-years (a person-year is the cumulative amount of time participants have been followed in a study), there were 497 hep C seroconversions in the studies included in the meta-analysis. This translated to an infection rate of 0.53 percent a year (or 0.53 per 100 person-years). Another way to understand this figure is to say that, if 1,000 HIV-positive non-IDU MSM were followed for one year, about five would contract hep C.

In 1991, the infection rate among the men studied was an estimated 0.42 percent per year. By 2010, this figure had tripled, to a 1.09 percent per-year infection rate. In 2012, the infection rate hit 1.34 percent.

“If the trend continues, current incidence of HCV infections may be as high as 1.92 new infections per 100 person-years—meaning, were we to follow 1,000 members of this cohort over the next year, we’d likely find that approximately 20 acquired HCV,” the study’s principal author, Holly Hagan, PhD, a professor New York University’s College of Nursing and codirector of the college’s Center for Drug Use and HIV Research (CDUHR), said in a press release.

The cohort of men included in this research is not necessarily a representative sample of the larger population of HIV-positive MSM. So such a rate of infection may not occur in this demographic across the board.

Hagan and her colleagues found that men were at greater risk of hep C infection if they engaged in condomless, receptive anal intercourse and if they had sex while taking non-injection drugs. One study found that crystal meth use was associated with a 28.6-fold increase in the risk of acquiring hep C.

Some men who were cured of hep C were then reinfected, and sometimes then reinfected again after another successful treatment. With a reinfection rate of 11 percent, those who were cured of hep C had a 20-fold greater likelihood of contracting hep C than the study group as a whole.

“All of this data indicates the existence of a subgroup of HIV-positive MSM with recurring sexual exposure to HCV in whom the rates may begin to approach the risk of HCV infection among [IDUs],” study co-author Ashly E. Jordan, MPH, an associate research scientist and project director of the HCV Synthesis Project at CDUHR, said in the same press release.

The researchers called for greater study into the causes of sexual transmission of hep C among HIV-positive MSM.

“Ideally, we’d like to see the development of an HCV prevention program for HIV-positive MSM that addresses both high-risk sex and drug use behavior,” said Hagan.

To read a press release about the study, click here.

To read the study abstract, click here.