A United States study of HIV infection among young gay men is a warning to New Zealand men not to make any assumptions about the HIV status of their sexual partners, the New Zealand AIDS Foundation says. Foundation senior researcher Peter Saxton says a new study from the USA has revealed high levels of undiagnosed HIV infection among young gay men. The study examined the behaviour of 5649 men-who-have-sex-with-men (MSM) aged under 30 across six US cities, and then compared these behaviours and beliefs to the young men's actual HIV status determined from blood samples. The study found that 10% of the young men were HIV positive, of whom three quarters (77%) were unaware they were infected. Of the men who were unaware of their infection, 59% perceived themselves to be at low risk for HIV infection, and 74% had previously tested HIV negative. Furthermore, half of the infected-unaware men had unprotected anal sex in the previous six months, with half of these men not using condoms because they either “knew” they were negative; “knew” their partners were negative; or they thought their partners were at low risk of being positive. Peter Saxton notes that while the prevalence of HIV is higher among United States MSM than New Zealand MSM, the findings reiterate the importance of not assuming sexual partners are HIV negative. “Our own analysis of the Gay Auckland Periodic Sex Survey 2004 showed that New Zealand MSM were making similar assumptions, to those reported in the US survey. One third of MSM in the Gay Auckland Periodic Sex Survey reported they still believed they were “definitely” HIV negative, even though they had had at least one instance of unprotected anal intercourse since their last HIV negative test. “What these studies show is that some sexual partners simply will not know they are HIV positive, even those who have previously tested negative, and those who sincerely believe they are negative or are at low risk of infection.” Saxton says the rates of unrecognised infection in the US study are higher than those found in another recent study of gay men in London, which found that a third of MSM infected with HIV were unaware of their infection. Citation: MacKellar, D. et al. (2005). Unrecognized HIV infection, risk behaviours, and perceptions of risk among young men who have sex with men. Journal of Acquired Immune Deficiency Syndrome. Vol. 38: 603-614. NZ AIDS Foundation - 13th May 2005