The number of HIV-negative men in Sydney who have unprotected casual sex with someone they believe to be of the same HIV status is on the rise, research to be presented next week shows.

Health authorities are also seeing an increase in the number of HIV-positive men who choose to have unprotected sex with other positive men.

The practice of choosing sex partners who appear to have the same HIV status, known as serosorting, is a strategy that could be increasing the risk of sexually transmissible infections.

Dr Limin Mao from the National Centre in HIV Social Research followed about 300 participants in the ongoing Health In Men (HIM) study of HIV-negative men between 2002 and 2005.

The proportion of casual partners these men perceived to be HIV-negative grew from six percent to 24 percent in that time.

More men are thinking that when they have unprotected anal intercourse with a casual partner they are more likely to be the same status as they are, Mao told Sydney Star Observer.

Mao will present the findings at the National Centre in HIV Social Research’s StigmaPleasurePractice conference at the University of NSW next week. The research is also due for publication in the medical journal AIDS next month.

Mao said HIM participants who reported unprotected casual anal sex were in the minority.

But the findings were still a concern because they suggested more HIV-negative men were using serosorting, which was an unreliable risk-reduction practice.

We’re sceptical of how effective this negative-negative serosorting is if applied as a risk-reduction strategy, Mao said.

[Casual partners] could be recent seroconverters not knowing themselves to be HIV-positive.

Growing rates of STIs in the gay community also made serosorting risky.

We’re just saying if people continually adopt this strategy to replace condom use in casual sex, it could be problematic, Mao said.

ACON chief executive Stevie Clayton told the Star separate research showed serosorting was also on the rise among Sydney’s HIV-positive community.

When you compare that to the stuff that Limin’s reporting from the HIM study, what it shows you really clearly is that serosorting is happening more and is possibly much more successful for positive guys, Clayton said.

If we’ve got two positive guys having sex, the risk of HIV transmission becomes a risk of superinfection, but not a risk of HIV transmission as we know it.

But we do think that [HIV-positive men] using serosorting rather than condoms is to some extent responsible for the large increase we’ve seen in syphilis in recent years.

Clayton said some men might be serosorting because they were tired of using a condom all the time or because they thought unprotected sex was better.

So they’re looking for ways to have sex without condoms but minimise their risk.

The challenge of course is to make sure they understand that there are very real risks still attached to serosorting.

Delegates at the StigmaPleasurePractice conference on 20 and 21 April will discuss current research and the themes of stigma and pleasure as they relate to drugs and sex.

The idea is to set up a bit of a dialogue with different perspectives, conference co-convenor Martin Holt told the Star.

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