In two recent studies, the majority of gay men had similar numbers of unprotected sexual encounters as straight men and women, countering theories that the main reason that gay men have higher infection rates than straight people is a drastic difference in sexual behavior.

Researchers analyzed factors such as how many sexual partners the participants had, the kind of intercourse they engaged in and estimates of how easily HIV is transmitted through vaginal versus anal sex. The study results suggested that straight men and women would have to have three times the number of sexual partners per year for their rates of HIV infection to match those of gay men.

The study also found that straight men and women would have to have five unprotected sexual partners per year for the epidemic to mirror that of gay men.

To end the HIV epidemic, gay men would have to have very much lower rates of unprotected sex than straight men and women currently have. The reason cited is that HIV transmission rates are much greater for anal sex, compared with vaginal sex.