Subtypes and Risk Behaviors Among Incident HIV Cases in the Bangkok Men Who Have Sex with Men Cohort Study, Thailand, 2006-2014.

HIV-1 incidence and prevalence remain high among men who have sex with men (MSM), and transgender women (TGW), in Thailand. To examine the link between epidemiologic factors and HIV-1 subtype transmission among Thai MSM, we compared covariates of infection with HIV CRF01_AE and other HIV strains among participants in the Bangkok MSM Cohort Study (BMCS). The BMCS was an observational cohort study of Thai MSM and TGW with up to 60 months of follow-up at 4 monthly intervals. Participants underwent HIV/sexually transmitted infections testing and provided behavioral data at each visit. Infecting viral strain was characterized by gene sequencing and/or multiregion hybridization assay. We correlated behavioral/clinical variables with infecting strain using Cox proportional hazards. Among a total of 1372 HIV seronegative enrolled participants with 4,192 person-years of follow-up, we identified 215 seroconverters between April 2006 and December 2014, with 177 infected with CRF01_AE and 38 with non-CRF01_AE subtype. Age 18-21 years (adjusted hazard ratio [AHR] 2.2, 95% confidence interval [CI]: 1.4-3.5), age 22-29 (AHR 1.6, 95% CI: 1.1-2.3), living alone (AHR 1.5, 95% CI: 1.1-2.1), drug use (AHR 2.2, 95% CI: 1.4-3.5), intermittent condom use (AHR 1.7, 95% CI: 1.3-2.3), any receptive anal intercourse (AHR 1.7, 95% CI: 1.2-2.4), group sex (AHR 1.5, 95% CI: 1.1-2.2), anti-herpes simplex virus type 1 (AHR 1.5, 95% CI: 1.1-2.1), and Treponema pallidum antibody positivity (AHR 2.5, 95% CI: 1.4-4.4) were associated with CRF01_AE infection. Age 18-21 years (AHR 5.1, 95% CI: 1.6-16.5), age 22-29 (AHR 3.6, 95% CI: 1.3-10.4), drug use (AHR 3.1, 95% CI: 1.3-7.5), group sex (AHR 2.4, 95% CI: 1.1-5.0), and hepatitis B virus surface antigen (AHR 3.6, 95% CI: 1.3-10.2) were associated with non-CRF01_AE infection. We observed several significant biological and behavioral correlates of infection with CRF01_AE and other HIV strains among Thai MSM. Divergence in correlates by strain may indicate differences in HIV transmission epidemiology between CRF01_AE and other strains. These differences could reflect founder effects, transmission within networks distinguished by specific risk factors, and possibly biological differences between HIV strains.