US study finds genital herpes near doubles risk of acquiring HIV in gay men

Whilst a recent meta-analysis has demonstrated a link between genital herpes and HIV acquisition in heterosexuals, the evidence that a similar relationship exists in relation to sex between men has been more equivocal. However, new data from the United States, where rising incidence of HIV infection is being observed in some gay male communities, suggest infection with the genital herpes virus (HSV-2) significantly increases the risk of gay men contracting HIV.

These new data were reported from a study following HIV-negative gay men in San Francisco, Chicago, Denver, New York, Seattle and Boston, and were presented at the 42nd ICAAC in San Diego yesterday.

The presence of certain sexually transmitted infections is known to raise the risk of HIV acquisition – amongst gay men, associations with rectal gonorrhoea and with urethritis have been demonstrated previously. In the current study, the authors sought to identify potentially modifiable risk factors for HIV transmission amongst gay men, the community where HIV prevalence and incidence is highest in the US.

Genital herpes is a common infection within this community, the reported prevalence being 30-50% in HIV-negative gay men, and around 80% in HIV-positive gay men. HIV-negative men who have sex with men, who reported having had anal sex in the past year, were recruited into a case-control study, and followed every six months for eighteen months. Information on their risk behaviours and symptoms of sexually transmitted infections was gathered via standardised interviews. Blood testing for HSV infection was performed at regular intervals to determine which men already had the genital herpes virus, and which acquired it during the period of follow-up. Similarly, the men’s HIV status was monitored. One hundred and sixteen men acquired HIV infection during the study period. These men were compared to a control group of 342 men who remained HIV-negative.

Overall, having prior genital herpes infection increased the risk of acquiring HIV by 80%, a 1.8-fold increased risk. In response, the authors recommend that strategies to reduce the acquisition of genital herpes should be evaluated for their potential also to reduce HIV transmission amongst gay men. Possible options include education, condom use and increased use of screening. The role of treatment which suppresses shedding of HSV-2 may too be worthy of evaluation. A late breaking presentation at this conference on Friday reported that daily valaciclovir reduced transmission of HSV-2 between heterosexual couples.

Simple Factsheets on genital herpes are available here at aidsmap.com in either html or pdf format.