Unexpectedly high HIV prevalence among female sex workers in Bangkok, Thailand in a respondent-driven sampling survey

The pattern of sex work in Thailand has shifted substantially over the last two decades from direct commercial establishments to indirect venues and non-venue-based settings. This respondent-driven sampling survey was conducted in Bangkok in 2007 among female sex workers (FSW) in non-venue-based settings to pilot a new approach to surveillance among this hidden population. Fifteen initial participants recruited 707 consenting participants who completed a behavioural questionnaire, and provided oral fluid for HIV testing, and urine for sexually transmitted infection (STI) testing. Overall HIV prevalence was 20.2% (95% confidence interval [CI] 16.3-24.7). Three-quarters of women were street-based (75.8%, 95% Cl 69.9-81.1) who had an especially high HIV prevalence (22.7%, 95% CI 18.2-28.4); about 10 times higher than that found in routine sentinel surveillance among venue-based FSW (2.5%). STI prevalence (Chlamydia trachomatis and Neisseria gonorrhoeae) was 8.7% (95% Cl 6.4-10.8) and 1.0% (95% Cl 0.2-1.9), respectively. Lower price per sex act and a current STI infection were independently associated with HIV infection (P < 0.05). High HIV prevalence found among FSW participating in the survey, particularly non-venue-based FSW, identifies need for further prevention efforts. In addition, it identifies a higher-risk segment of FSW not reached through routine sentinel surveillance but accessible through this survey method.