Risk Factors for HIV Infection among Young Thai Men during 2005-2009.

Background: Thailand is one of several countries with a continuing generalized HIV epidemic. We evaluated the risk factors for HIV prevalence among 17-29 year old men conscripted by a random process into the Royal Thai Army (RTA) in 8 cohorts from 2005-2009.

Methods: A series of case-cohort studies were conducted among the male RTA conscripts who had been tested for HIV seroprevalence after they were inducted. Men who were HIV positive were compared with a systematic random sample (1 in 30-40) of men from the total population of new conscripts. Each subject completed a detailed risk factor questionnaire.

Results: A total of 240,039 young Thai men were conscripted into the RTA and were screened for HIV seroprevalence between November 2005 and May 2009. Of 1,208 (0.5%) HIV positive cases, 584 (48.3%) men were enrolled into the study. There were 7,396 men who were enrolled as a comparison group. Among conscripts who had an education lower than a college-level, the independent risk factors for HIV infection were age in years (AOR 1.38, 95% CI 1.28-1.48), a history of sex with another man (AOR 3.73, 95% CI 2.70-5.13), HCV infection (AOR 3.89, 95% CI 2.56-5.90), and a history of sex with a female sex worker (FSW) (AOR 1.35, 95% CI 1.10-1.66). Among conscripts who had a college degree, the independent risk factor for HIV infection was a history of sex with another man (AOR 23.04, 95% CI 10.23-51.90). Numbers of sexual partners increased and the age at first sex, as well as the use of condoms for sex with a FSW decreased in successive cohorts.

Conclusion: The HIV seroprevalence among cohorts of 17-29 years old men has remained at about 0.5% overall during 2005-2009. The most significant behavior associated with HIV prevalence was a history of sex with another man. Our data indicate continuing acquisition of HIV among young men in Thailand in recent years, especially among men with a history of same sex behavior.