HIV is hyperendemic among men who have sex with men in San Francisco: 10-year trends in HIV incidence, HIV prevalence, sexually transmitted infections and sexual risk behaviour S Scheer, 1 T Kellogg, 1 J D Klausner, 1 S Schwarcz, 1 G Colfax, 1 K Bernstein, 1 B Louie, 1 J W Dilley, 2 J Hecht, 3 H-H M Truong, 4 M H Katz, 1 W McFarland 1 1 San Francisco Department of Public Health, San Francisco, California, USA; 2 AIDS Health Project, University of California, San Francisco, California, USA; 3 The STOP AIDS Project, San Francisco, California, USA; 4 Center for AIDS Prevention Studies, University of California, San Francisco, California, USA Correspondence to: Dr S Scheer, San Francisco Department of Public Health, 25 Van Ness Avenue, Suite 500, San Francisco, CA 94102-6033, USA; Susan.Scheer@sfdph.org Accepted 2 September 2008 ABSTRACT Objectives: To evaluate trends in the HIV epidemic among men who have sex with men (MSM) in San Francisco and the implications for HIV prevention. Methods: An ecological approach assessed temporal trends in sexual risk behaviour, sexually transmitted infections (STI), HIV incidence and prevalence from multiple data sources between 1998 and 2007. Results: By 2007, there were over 13 000 HIV-infected MSM living in San Francisco. No consistent upward or downward temporal trends were found in HIV incidence, newly reported HIV cases, AIDS deaths, proportion of AIDS cases using antiretroviral therapy, rectal gonorrhoea or primary and secondary syphilis cases among MSM during the study period. Trends in indicators of sexual risk behaviour among MSM were mixed. Overall, unprotected anal intercourse (UAI) increased in community-based surveys. Among HIV-positive MSM, no significant trends were noted for UAI. Among HIV-negative MSM, UAI with unknown serostatus partners decreased but increased with potentially discordant serostatus partners. Among MSM seeking HIV testing, increases were noted in insertive UAI at anonymous testing sites and at the STI clinic, in receptive UAI at anonymous test sites and in receptive UAI with a known HIV-positive partner at the STI clinic. Conclusions: Temporal trends in multiple biological and behavioural indicators over the past decade describe a hyperendemic state of HIV infection among MSM in San Francisco, whereby prevalence has stabilised at a very high level. In the absence of new, effective prevention strategies this state will persist. Over the past decade, a resurgence of sexual risk behaviour, sexually transmitted infections (STI) and/ or incident HIV infections have been reported among men who have sex with men (MSM). 1–3 These phenomena were first noticed in cities of the industrialised world with large gay communities in North America, Europe and Australia, and later Asian cities with emerging economies, such as Bangkok and Beijing, also noticed increases in HIV prevalence. 45 As in the beginning of the HIV epidemic, MSM continue to be disproportionately affected. San Francisco was one of the first cities to identify AIDS cases among MSM in the early 1980s. 6 Since then, the HIV epidemic has been tracked through multiple studies, including cohorts pre-dating and overlapping the discovery of AIDS, HIV and AIDS case reporting, STI surveillance, cross-sectional behavioural and seroprevalence sur- veys and community-based programmatic data. From these data sources, a history of the epidemic among MSM in San Francisco can be charted. Data from a hepatitis B vaccine trial and back calcula- tion of early AIDS cases show that HIV transmis- sion began and accelerated in the late 1970s, with a peak incidence of new infections already evident in the early 1980s. 7 By the mid to late 1980s, rapid declines in sexual risk behaviour, STI and HIV incidence among MSM were noted. 8 Despite this apparent success, transmission continued, albeit at a lower level, into the 1990s. The pivotal year of 1995 saw the advent of highly active antiretroviral therapy (ART), which greatly improved survival with AIDS and brought hope that HIV transmis- sion would be reduced by therapeutic viral suppression. However, the period of rapid scale up of highly active ART in San Francisco (1995– 2001) was paralleled by a resurgence in sexual risk behaviour, STI and HIV incidence. 9 The resurgence may have been driven by a number of factors, including the rising number of MSM living with HIV, the resumption of sexual activity among previously ill MSM with HIV, the increase in STI among MSM with HIV and the increase in sexual risk behaviour and STI among other MSM. ‘‘ART optimism’’, the decreased concern over HIV infec- tion as a result of treatment successes, may also have contributed to the resumption in sexual risk behaviour. 10 We previously reported that this resurgence may have abated in San Francisco during the mid-2000s, possibly partly due to increased ‘‘serosorting’’ whereby MSM were choosing partners of concordant HIV status for unprotected sex. 11 The potential role of serosorting was supported by a high level of HIV testing, continued rises in STI and overall unprotected anal intercourse (UAI), but declines in UAI with partners of unknown serostatus. The period was also marked by intensified prevention efforts, notably prevention programmes for HIV-positive MSM, innovative approaches to screening and treating STI and programmes addressing substance use associated with unsafe sexual behaviour. 12 The questions now at hand are: what are the current trends in the HIV epidemic among MSM and what are their implications for future HIV prevention? Because of the high concentration of MSM and well-established systems for collecting data, San Francisco has been among the cities Original article Sex Transm Infect 2008;84:493–498. doi:10.1136/sti.2008.031823 493 on 21 November 2008 sti.bmj.com Downloaded from