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Subtypes and risk behaviors among incident HIV cases in the Bangkok Men Who Have Sex with Men Cohort Study, 2006-2012

Lam, Caitlin Rebecca (2013)
Master's Thesis (45 pages)
Committee Chair / Thesis Adviser: Sullivan, Patrick S
Committee Members: Curlin, Marcel (Thai MoPH-US CDC); Holtz, Timothy (Thai MoPH-US CDC);
Research Fields: Health Sciences, Public Health; Health Sciences, Epidemiology
Partnering Agencies: CDC
Keywords: HIV/AIDS; Men who have sex with men; HIV subtypes; sexual risk behaviors; Bangkok; Thailand
Program: Rollins School of Public Health, Epidemiology (Global Epidemiology)
Permanent url:



Recently, HIV transmission rates in Thailand have declined partly due to HIV policies established by the Thai Ministry of Public Health (MoPH). Nevertheless, within the men who have sex with men (MSM) community, the incidence and prevalence are alarmingly high. These high infection rates can partly be attributed to the greater prevalence of high-risk behaviors in this community. Thus, it is critical that we improve our knowledge of the epidemiology within this high-risk group and their behaviors, in order to effectively respond to the disproportionate disease burden in this population. We sought to describe the association between HIV strains and risk behaviors among urban Thai MSM seroincident HIV cases enrolled in the Bangkok MSM Cohort Study (BMCS).


The BMCS is an open longitudinal cohort study, with a maximum of 60 months of follow-up at 4-monthly intervals. Study variables included HIV subtype, HIV risk behaviors and sexually transmitted infection laboratory variables. The outcome variable was a dichotomoized measure of HIV strain, either circulating recombinant form (CRF) 01_AE or non-CRF01_AE. HIV strain was determined at time of seroconversion. Bivariate and multivariate analyses were conducted separately for each strain (non-CRF01_AE used an inclusion criteria of p-value £0.25 due to the small sample size) using Cox proportional hazard to assess the association between behavioral risk factors, laboratory variables, and incident HIV infection by subtype.


A total of 188 seroconverters were included in this analysis: 154 were CRF01_AE strain and 34 were non-CRF01_AE strain, enrolled from April 2006 till May 2012. In the final model, use of drugs to enhance sexual pleasure (adjusted hazard ratio [AHR] 0.45, 95% CI: 0.28-0.73), intermittent condom use (AHR 1.82, 95% CI: 1.32-2.51), receptive only or both anal sex positions (AHR 1.92, 95% CI: 1.34-2.76), and HSV-1 (AHR 1.52, 95% CI: 1.09-2.11) and T. pallidum positivity (AHR 0.35, 95% CI: 0.20-0.62) were significantly associated with CRF01_AE seroconversion. Younger age, 18-21 year olds (AHR 3.65, 95% CI: 1.06-23.53) and 22-29 year olds (AHR 3.03, 95% CI: 1.04-8.82), use of club drugs (AHR 2.22, 95% CI: 0.89-5.52), group sex (AHR 2.32, 95% CI: 1.08-5.00) and HBV surface antigen positivity were significantly associated with non-CRF01_AE seroconversion.


There were some differences in the risk behaviors associated with incident CRF01_AE and non-CRF01_AE HIV subtype infection. Continued focus on this high-risk group, especially for young MSM, where most of incident cases are originating from, will be necessary in order to decrease HIV prevalence and transmission rates in future years.

Table of Contents

Table of Contents

Literature Review...8
Future Directions...26

Table 1. Study variables...34
Table 2. Demographic and behavioral risk factor results...35
Table 3. Bivariate and multivariate CRF01_AE subtype results...36
Table 4. Bivariate non-CRF01_AE subtype results...39


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