HIV and syphilis prevalence among men who have sex with men: a cross-sectional survey of 61 cities in China.

(See the Editorial Commentary by Muessig and Cohen on pages 310–3.) Prevalence estimates of human immunodeficiency virus (HIV) among men who have sex with men (MSM) in developing Asian countries are high: 7.8% in Cambodia, 9.0% in Indonesia, 14.7% in India, and 24.6% in Thailand [1]. In India, prevalence varies geographically from 7.5% to as high as 20.9% [2], and in Thailand, HIV prevalence has increased rapidly—17.3% in 2003, 28.3% in 2005, and 30.8% in 2007 [3]. As HIV susceptibility and/or infectiousness is associated with the presence of other sexually transmitted infections such as syphilis [4], it is not surprising that syphilis is also a major public health issue among MSM in developing Asian nations—4.3% in Indonesia [5], 8.4%–14% in India [2], and 33% among those newly diagnosed with HIV in Thailand [6]. In China, several meta-analyses of HIV and syphilis prevalence among Chinese MSM have been published [7–10]. In 2009, Gao et al reported a pooled HIV prevalence of 2.5% and a pooled syphilis prevalence of 9.1% for studies conducted during 2001–2008 [7]. In 2011, Li et al reported a range of 3.2%–15.8% for HIV prevalence for studies conducted during 2005–2008 [8]. Also in 2011, Chow et al reported HIV prevalence of 5.3% for 2007–2009 [9] and 4.7% for 2007–2008, and syphilis prevalence of 13.5% for the same time period [10]. However, it is unclear how generalizable these study findings are owing to relatively small sample sizes or few study sites. Additionally, we find only 2 studies describing the nationwide geographical distributions of HIV and syphilis prevalence, one reporting that HIV prevalence among MSM is significantly higher over time in the Southwest region only and another finding that HIV and syphilis prevalence is correlated in the Northeast and East regions only [9, 10]. Furthermore, a few studies have suggested that there are different segments within the Chinese MSM community (one ethnographic study identifying as many as 20), which have very little overlap in their behavioral characteristics and social circles [11, 12]. It is in this context that we have undertaken the largest study of HIV and syphilis prevalence among MSM in the world, surveying and testing a total of 47 231 MSM. Our primary aim was to directly obtain a reliable measure of the current magnitude and geography of the HIV and syphilis epidemics among MSM in China, testing the hypothesis that HIV and syphilis prevalences are high, but with unique geographical distributions. We also hypothesized that there are several segments within the MSM population that have different characteristics; thus, our secondary aim was to identify and describe a few of these subgroups.