Sexual activity is a cause of hepatitis C virus (HCV) transmission, at least among men living with HIV who have sex with men, according to a study performed by researchers at Mount Sinai Hospital and published in the CDC’s Morbidity and Mortality Weekly Report (MMWR).

HCV is most commonly transmitted through injection drug use. Though the role of sexual transmission has not been well defined, reports over the past decade-mainly from Europe-have implicated sexual transmission of HCV among HIV-positive men who have sex with men (MSM).

To gain an understanding of the risk factors associated with sexual transmission in a U.S. population, Daniel Fierer, MD, of Mount Sinai Medical Center in New York City surveyed 22 HIV-positive MSM who’d been infected by HCV within the previous 12 months and who reported no injection drug use. These were contrasted with with a control group of 53 MSM without HCV infection. Both groups filled out questionnaires regarding their recent sexual activity and drug use.

In a strict analysis that accounted for all risk factors accounted for in the study, Fierer’s group found that the men with HCV infection were 23 times more likely than the control group to have had unprotected receptive anal sex, with ejaculate. Moreover, they were 29 times more likely to have sex while high on crystal meth.

“While hepatitis C is not sexually transmitted among stable heterosexual couples, this is clearly not the case among HIV-infected MSM in New York City,” said Fierer in a press release. “MSM, and to some extent their health care providers, are generally not aware that having unprotected receptive sex can result in HCV infection.  The good news is that the cure rate for new HCV infections is very high with early treatment, but without regular testing of the men at risk, these largely asymptomatic infections may be missed and this opportunity lost.”

Fierer went on to advise HIV-positive MSM to use condoms and avoid crystal meth. He also suggested that health care providers screen such men for hepatitis C, and that information on the risks of sexually transmitted HCV should be incorporated into sex education and outreach programs.

An editorial note accompanying the MMWR report points out possible sources of bias in the report, such as the possible failure to note injection drug use. However, the same editorial suggests this report does not exist in a vacuum, noting the existence of other studies drawing similar conclusions.