Evidence of an explosive epidemic of HIV infection in a cohort of men who have sex with men in Thailand.

OBJECTIVE: To assess HIV-prevalence, incidence and risk factors in a cohort of men who have sex with men (MSM) in Bangkok.
DESIGN: : Cohort study with 4-monthly follow-up visits conducted between April 2006 and July 2012 at a dedicated study clinic in a central Bangkok hospital. Participants were 1744 homosexually active Thai men, at least 18 years old and residents of Bangkok.
METHODS: Men were tested for HIV-infection at every study visit and for sexually transmitted infections at baseline. Demographic and behavioural data were collected by audio-computer-assisted self-interview. Logistic regression analysis was used to evaluate risk factors for HIV-prevalence and Cox proportional hazard analysis to evaluate risk factors for HIV-incidence.
RESULTS: Baseline HIV-prevalence was 21.3% (n = 372) and 60 months cumulative HIV-incidence was 23.9% (n = 222). Overall HIV-incidence density was 5.9 per 100 person-years. Multivariate risk factors for HIV-prevalence were older age, secondary/vocational education (vs. university or higher), employed or unemployed (vs. studying), nitrate inhalation, drug use for sexual pleasure, receptive anal intercourse, history of sexual coercion, no prior HIV-testing, and anti-HSV-1 and 2 and Treponema pallidum positivity at baseline. Multivariate risk factors for HIV-incidence were younger age, living alone or with roommate (vs. with a partner or family), drug use for sexual pleasure, inconsistent condom use, receptive anal intercourse, group sex, and anti-HSV-1 and 2 and T. pallidum positivity at baseline. Having no anal intercourse partners was inversely associated with HIV-incidence.
CONCLUSION: The high HIV prevalence and incidence in this cohort of Bangkok MSM documents an explosive epidemic. Additional preventive interventions for MSM are urgently needed.