WASHINGTON, Sep 7 2012 (IPS) – Unlike the flattening or even declining rates of HIV infection among nearly all other communities, the epidemic among gay men globally is rapidly expanding.
But according to new research, the reason for this fast expansion is biological, not behavioural, thus countering some of the core priorities of traditional AIDS funding.
“The trajectory of HIV epidemics among MSM” – men who have sex with men – “is expanding virtually everywhere we look, in low-, middle- and high-income countries, and across all regions,” Chris Beyrer, a professor of international health, told a panel discussion here on Thursday.
“Much of this comes down to a fundamental biological reality: it’s not about gender but about the gut.”
Beyrer, who contributed to a recent groundbreaking special issue of The Lancet, the British medical journal, on HIV in MSM, says that researchers have found that the HIV virus is far more efficiently transmitted through the gut, hence leading to a far higher transmission probability in anal sex, for either a man or a woman – around 18 times more likely than through vaginal transmission.
Further, because gay men can switch sexual roles in a way that is impossible among heterosexual couples – acting as both the acquisition and transmission partner – the efficiency of transmission among MSM networks appears to be far higher than previously understood.
In a hypothetical MSM group in which men did not alternate their sexual roles, Beyrer reports that HIV incidence could be reduced by up to 55 percent.
“The network-level effects are really trumping the individual level,” he says. “So, people who have modest individual-level risks but who are having sex in high-risk networks and communities have very high lifetime acquisition risks.”
Taken together, the ramifications of these two findings are startling. These two factors, the new research suggests, account for a full 98 percent of the difference between HIV epidemics among MSM and heterosexual populations.
“What this means is that all the things that we had been focusing on – multiple partners, behaviours, etc. – only explain about two percent” of new infections, Beyrer says. “We have got to have programmes that are more responsive to the actual realities of transmission – focusing on the tail of the problem is unlikely to have the impacts we’d like to see.”
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