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Seroadaptive behaviours among men who have sex with men in San Francisco: the situation in 2008
  1. Jonathan M Snowden1,
  2. H Fisher Raymond2,
  3. Willi McFarland3
  1. 1School of Public Health, University of California, Berkeley, California, USA
  2. 2San Francisco Department of Public Health, San Francisco, California, USA
  3. 3San Francisco Department of Public Health and University of California, San Francisco, California, USA
  1. Correspondence to Dr Willi McFarland, AIDS Office, 25 Van Ness Avenue, Suite 500, San Francisco, CA 94102-6033, USA; willi_mcfarland{at}


Objectives To assess changes in seroadaptive behaviours among men who have sex with men (MSM) in San Francisco over the past 4 years.

Methods 461 MSM were recruited in 2008 as the second wave of the US National HIV Behavioural Surveillance (NHBS) survey in San Francisco. Participants were classified into patterns of seroadaptive behaviours based on reported sexual practices (ie, episodes of insertive and receptive anal sex), condom use, HIV serostatus and partners' serostatus for up to five partners in the preceding 6 months. The prevalence of seroadaptive behaviours was compared with the first wave of NHBS, which used identical methods in 2004.

Results In 2008, 33.7% of HIV-negative and 18.9% of HIV-positive MSM used condoms 100% of the time; nearly half (48.0%) of HIV-negative MSM and two-thirds (66.7%) of HIV-positive MSM had unprotected anal intercourse (UAI). Collectively, seroadaptive behaviours comprised the most common form of risk management; 40.5% of HIV-negative MSM and 51.1% of HIV-positive MSM engaged in some form of seroadaptation, the most common being ‘pure serosorting’ (all UAI with same serostatus partners) reported by 27.5% of HIV-negative MSM and 22.2% of HIV-positive MSM. None of these behaviours were significantly different from their corresponding measures in 2004.

Conclusions Seroadaptation continues to describe the prevailing form of sexual risk management for MSM in San Francisco, suggesting that these behaviours are not novel and require careful measurement to gauge the true potential for the spread of HIV, and nuanced prevention messages to reduce risk.

  • Seroadaptation
  • serosorting
  • HIV
  • men who have sex with men
  • epidemiology
  • gay men
  • HIV
  • sexual behaviour
  • surveillance

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Epidemiological research during the past decade suggests that in many parts of the world, men who have sex with men (MSM) are practising increasing levels of unprotected anal intercourse (UAI) with concomitant increases in sexually transmitted infection (STI) and, in some places, new HIV diagnoses.1–3 However, in some areas increases in UAI and STI were not accompanied by increases in HIV incidence, suggesting that ‘serosorting’ (ie, UAI between partners of the same HIV serostatus) was occurring.2–8 We previously described a range of sexual risk management behaviours collectively called ‘seroadaptation’ that varied according one's own and one's partners' serostatus and measured their prevalence in MSM in San Francisco in 2004.8 In this report, we applied the seroadaptation framework to the 2008 wave of the same behavioural surveillance survey to assess changes in seroadaptive behaviours.


Data originate from the National HIV Behavioural Surveillance (NHBS) survey conducted among MSM in San Francisco in 2008. As part of a standardised biological and behavioural surveillance system coordinated by the US Centers for Disease Control and Prevention, we used time-location sampling (TLS) methods identical to those used in the 2004 wave of NHBS to recruit MSM. Details of TLS and NHBS methods have been described previously.8 9 In brief, formative research mapped venues where MSM congregate and the periods of high attendance to generate a list of venue-day-times (VDT) from which a random sample of VDT was drawn. At each randomly selected VDT, research staff systematically intercepted men entering a predetermined area, assessed eligibility, and if eligible, invited participation. Identifying subjects as gay, bisexual or MSM was not an eligibility criterion, though we only included MSM in this analysis.

We categorised the men in this sample using the same seroadaptation categories described in the 2004 analysis8 and summarised in table 1. Men were classified based on their consistent pattern of sexual behaviour with their most recent five sexual partners in the past 6 months in a hierarchical framework from ‘abstainers’ (no anal sex), ‘100% condom users’, ‘pure serosorting’ (all UAI partners were of the same HIV serostatus), ‘negotiated safety’ (UAI only with a primary partner of negative serostatus, HIV-negative men only), ‘condom serosorting’ (UAI only with same serostatus partners, otherwise condom use) and ‘seropositioning’ (UAI as insertive only for HIV-negative MSM, receptive only for HIV-positive MSM). Those not categorised into the above behaviours were classified as having engaged in ‘risky’ UAI.

Table 1

Comparison of seroadaptive behaviours among men who have sex with men (MSM), San Francisco, 2004–8

The study was reviewed and approved by the Committee on Human Research at the University of California, San Francisco.


Of 461 MSM enrolled in 2008, 100% condom use was practised by one-third of HIV-negative men (33.7%) and by less than one in five HIV-positive men (18.9%) (table 1). Collectively, seroadaptation comprised the most common risk management behaviours practised by HIV-negative and HIV-positive men (40.5% and 51.1%, respectively). Among HIV-negative men, no individual seroadaptive behaviour was more prevalent than 100% condom use. Of seroadaptive behaviours, pure serosorting was most common (27.5%), followed by seropositioning (6.5%), condom serosorting (3.8%) and negotiated safety (2.7%). The proportion of HIV-negative MSM engaging in risky UAI was 7.5%. Among HIV-positive MSM two seroadaptive behaviours were as common or more common than 100% condom use: pure serosorting (22.2%) and seropositioning (18.9%). The proportion of HIV-positive men practising risky UAI was 15.6%. There were no statistical differences in the prevalence of seroadaptive behaviours of MSM measured in 2008 compared with 2004 for HIV-negative or HIV-positive men (χ2 test, p=0.90 and p=0.85, respectively).


Seroadaptive behaviours were collectively more common than consistent condom use among MSM in San Francisco. Because a hallmark of seroadaptation is an acceptance of UAI in certain circumstances, on the face of it the majority of MSM were engaging in sexual risk behaviour as defined by inconsistent condom use. However, only a minority reported engaging in UAI with a person of opposite or unknown HIV serostatus (ie, not consistent condom use or seroadaptation). Understanding the true potential for the spread of HIV requires a knowledge of one's own serostatus, one's partners' serostatus, the relative risks of these corresponding sexual behaviours and their frequencies with each partner. Other researchers additionally emphasise the importance of true serostatus disclosure within partnerships.10 Given these considerations, our indicators of seroadaptation must be interpreted with caution. Nonetheless, compared with identical measures from 4 years ago, we found no evidence of any changes, suggesting a continued primary reliance on these sexual risk management behaviours. These findings raise the challenge of how best to provide information and support to maximise the true risk reduction benefit to men choosing seroadaptive behaviours, while simultaneously continuing to provide information to MSM who wish to use condoms consistently.

Key messages

  • Levels of consistent condom use, seroadaptive behaviours and at-risk unprotected anal intercourse remained unchanged among men who have sex with men (MSM) in San Francisco from 2004 to 2008.

  • Collectively, seroadaptation comprised the most common HIV risk management behaviours reported by HIV-positive (51.1%) and HIV-negative (40.5%) MSM.

  • Although the majority of MSM in San Francisco practise unprotected anal intercourse, only a minority are engaging in the most risky sexual behaviour.


The authors would like to acknowledge support from the Centers for Disease Control and Prevention (CDC) for National HIV Behavioural Surveillance cooperative agreement U62/PS000961.



  • Funding Funding was provided by the Division of HIV/AIDS Prevention, CDC (U62/PS000961). The CDC had no other role in the creation of this paper and the views expressed herein are those of the authors alone. Other Funders: US Centers for Disease Control and Prevention.

  • Competing interests None.

  • Ethics approval This study was conducted with the approval of the Committee on Human Research, University of California, San Francisco.

  • Provenance and peer review Not commissioned; externally peer reviewed.