Bridging populations-sexual risk behaviors and HIV prevalence in clients and partners of female sex workers, Bangkok, Thailand 2007.

The aim of this study is to estimate HIV prevalence and assess sexual behaviors in a high-risk and difficult-to-reach population of clients of female sex workers (FSWs). A modified variation of respondent-driven sampling was conducted among FSWs in Bangkok, where FSWs recruited 3 FSW peers, 1 client, and 1 nonpaying partner. After informed consent was obtained, participants completed a questionnaire, were HIV-tested, and were asked to return for results. Analyses were weighted to control for the design of the survey. Among 540 FSWs, 188 (35%) recruited 1 client, and 88 (16%) recruited 1 nonpaying partner. Clients' median age was 38 years. HIV prevalence was 20% and was associated with younger age at first sexual experience [relative risk (RR) = 3.10, 95% confidence interval (CI) 1.16-8.24] and condom use during last sexual encounter with regular partner (RR = 3.97, 95% CI 1.09-14.61). Median age of nonpaying partners was 34 years, and HIV prevalence was 15.1%. There were 56 discordant FSW-client pairs and 14 discordant FSW-nonpaying partner pairs. Condom use was relatively high among discordant FSW-client pairs (90.1%) compared to discordant FSW-nonpaying partner pairs (18.7%). Results suggest that sexual partners of FSWs have a high HIV prevalence and can be a bridge for HIV transmission to other populations. Findings also highlight the importance of initiating surveillance and targeted programs for FSW partners, and demonstrate a recruitment method for hard-to-reach populations.