As antiretroviral drugs become more widely available, many who study HIV worry that people are taking fewer precautions to keep from getting the virus in the first place. In this multiyear survey, British researchers asked gay men about their sexual behavior and HIV status.

What the researchers wanted to know: How is sexual behavior changing among HIV-positive gay men?

What they did: Researchers visited clubs, bars, and saunas across London where gay men socialize to conduct a behavioral survey every year from 1996 to 2000. Participants filled out a questionnaire on their HIV testing history, HIV status, sexual behavior, and use of sexual health services. In 2000, the researchers also carried out anonymous saliva tests for HIV. They calculated sexual risk based on how often men reported having had unprotected anal intercourse in the last year.

What they found: Over the five years of the survey, the number of men having unprotected anal sex increased, as did the number having unprotected sex with men whose HIV status was unknown or different from their own. Eleven percent of the men were HIV positive, one third of whom didn't know. HIV-positive men were particularly likely to have had high-risk sex in the last year.

What this study means to you: Having unprotected anal sex increases the risk of spreading HIV; knowing about the trends makes it easier to design public health campaigns.

Caveats: The study only covers men who go to gay venues, so it doesn't represent all gay men. Also, it depends on men to report their own behavior accurately.

Find out more: AIDS info from the National Institutes of Health: http://www.aidsinfo.nih.gov

All about AIDS at http://www.thebody.com

Read the article: Dodds, J.P. et al. Increasing Risk Behaviour and High Levels of Undiagnosed HIV Infection in a Community Sample of Homosexual Men. Sexually Transmitted Infections. June 2004, Vol. 80, pp. 236–240.