No evidence of an increase in serosorting amongst HIV-negative gay men in London

The percentage of HIV-negative men engaging in unprotected anal sex with other HIV-negative men (serosorting) has not increased in London in recent years, according to research published in the January 11^th edition of AIDS. This finding is in contrast to a recent study in Sydney that found evidence of serosorting amongst HIV-negative men, and to studies conducted in numerous cities, London amongst them, that have found that HIV-positive men are increasingly serosorting.

The consistent and correct use of condoms for penetrative sex is a highly effective method of HIV prevention. Yet many individuals find condom use difficult to maintain in the longer term and have adopted other personal HIV prevention strategies. One such strategy increasingly reported by HIV-positive gay men is serosorting – this involves HIV-positive gay men choosing only to have unprotected anal sex with casual partners who are also HIV-positive. Although there is no risk of primary HIV transmission occurring in such encounters, there are other health concerns, including sexually transmitted infections, hepatitis C infection, and HIV superinfection. Studies conducted in Europe, the United States, Canada and Australia have all found evidence of serosorting by HIV-positive gay men.

Although serosorting may be a viable HIV prevention strategy for HIV-positive men (because they know their HIV status and can mutually disclose), it is much more problematic for HIV-negative men. This is because their perceived HIV status may differ from their actual HIV status and because they cannot reliably establish that their casual sexual partners have the same HIV status.

A study conducted in Sydney recently found evidence of an increase in serosorting by HIV-negative men, a finding that is of concern to HIV prevention workers. In light of the Sydney study, investigators wished to see if there was any evidence of an increase in serosorting among HIV-negative men in London in recent years. They therefore examined trends in serosorting amongst HIV-negative men who participated in an annual survey conducted at central London gyms designed to assess, amongst other things, HIV risk behaviours.

Men were asked if they had had unprotected anal sex in the previous three months and to specify if this was with a main or casual partner. They were also asked to provide details of their own HIV status and to say if they knew what the HIV status of the partner(s) with whom they had unprotected anal sex was.

Complete information on HIV status and sexual risk behaviour was available for 3,430 HIV-negative men for surveys conducted between 1998 and 2005.

There was no significant change in the percentage of HIV-uninfected men who said that they had had unprotected anal sex only with casual partners, who, like them, were HIV-negative. By contrast, there was a significant increase in the number of HIV-positive gay men reporting unprotected anal sex in casual encounters with other HIV-positive gay men during this period (p < 0.01).

The investigators also found that between 1998 and 2001, there was a significant increase in the number of HIV-negative men reporting unprotected anal sex with a casual partner whose HIV status they did not know or who were HIV-positive (p < 0.01). This percentage then stabilised between 2002 and 2005. Yet, for HIV-negative men who only reported unprotected anal sex with other HIV-negative men, there was no significant trend in either the period 1998 – 2001 or 2002 – 2005. In all the years studied, the vast majority (80% - 90%) of HIV-negative men reporting unprotected anal sex with a casual partner, said they had engaged in this behaviour with men were either of unknown HIV status or HIV-positive.

Detailed data from the 2003 gyms survey were provided by the investigators. Of the 334 HIV-negative men who complete the survey that year, less than 1% said that they had intentionally sought unprotected anal sex with a casual HIV-negative partner.

Investigators also looked to see if HIV-negative men, like men with HIV, were using the internet to serosort. Evidence from a study conducted at an HIV testing clinic, and answers to the gym surveys, showed that HIV-negative men were no more likely to meet other HIV-negative casual partners online for unprotected sex than offline.

“The percentage of HIV-negative gay men who reported serosorting with casual unprotected anal intercourse partners did not increase between 1998 and 2005”, conclude the investigators. They note that this is in marked contrast to the findings of the study conducted in Sydney. This suggests to the investigators that “there may be heterogeneity between cities and communities, possibly reflecting different levels of HIV testing.”