HIV-1 subtype E incidence and sexually transmitted diseases in a cohort of military conscripts in northern Thailand

Objectives: To determine the rate of and risk factors for HIV-1 seroconversion and describe sexually transmitted disease (STD) prevalence rates for young men in northern Thailand. Methods: Data were collected from self-administered questionnaires and serologic testing at enrollment In a prospective study in 1991 and at follow-up after 6, 17, and 23 months on a cohort of 1115 men selected by lottery for military conscription. Results: A total of 14 men seroconverted to HIV-I envelope subtype E. The overall HN-I incidence rate was 1.1 (95% confidence interval [CI], 0.6-1.8) per 100 person-years (PY) of follow-up. However, the rate was 2.0/100 PY for conscripts from the upper northern subregion of Thailand compared with 0.5/100 PY from other regions (adjusted rate ratio [RR] = 2.69; 95% CI, 0.8-12.2). On multivariate analyses, the behavioral factors associated with HIV-I seroconversion were frequency of sex with female sex workers (FSWs; p =.04), receptive anal sex (adjusted RR = 6.73; 95% CI, 1.8-21.7), and large amount of alcohol consumption (adjusted RR = 3.12; 95% CI, 1.0-10.9). Genital ulceration was the STD most strongly associated with seroconversion. The prevalence of serologic reactivity to syphilis, Hsemophilus ducreyi, and herpes simplex virus type 2 increased with greater frequency of sex with FSWs and was generally higher for men from the upper north. Conclusions: Young men in northern Thailand are at high risk for HIV-1, primarily through sex with FSWs; and other STDs are highly associated with HIV-1 incidence. As HIV-I infection extends into the general population, intervention programs are needed to address the problem of sexual transmission apart from commercial sex venues.