Overland heroin export routes have been associated with dual epidemics of injecting drug use and HIV infection in three Asian countries and along four routes. Molecular epidemiology is useful for mapping heroin routes. Single country narcotics and HIV programs are unlikely to succeed unless the regional narcotic-based economy is addressed.

CRF01_AE and subtype B have dominated the HIV-1 epidemic in Thailand since 1989. We reported a new circulating recombinant form of HIV-1, CRF15_01B, as well as other unique CRF01_AE/B recombinants among prevalent HIV infections in Thailand. We sought to study this challenging molecular picture through assessment of subtypes among recent HIV-1 seroconverters in northern Thai drug users. A total of 847 HIV-1 seronegative drug users (342 IDU and 505 non-IDU) were enrolled, from 1999 to 2002, in a prospective study; 39 HIV-1 incident cases were identified and characteristics were collected. The overall HIV-1 incidence rate was 2.54/100PY, but it was 10.0/100PY among male IDU. HIV was strongly associated with injection history; 38 of 39 seroconverters gave a history of IDU. A near full-length genome of HIV-1 was recovered by PCR amplification and sequenced from peripheral mononuclear cell extracted DNA of 38 seroconverters. Phylogenetic analysis revealed that 33 (86.8%) were CRF01_AE and 5 (13.2%) were CRF01_AE/B recombinants. These recombinants had different structure but shared some common breakpoints, indicating an ongoing recombination process. Recombinant infection increased with year of sampling (0 to 57.1%). The molecular epidemiology of HIV-1 among drug users in northern Thailand has thus entered a new era. CRF01_AE remains predominant while pure subtype B is becoming rare, and now a substantial component of the epidemic. These findings support the need for CRF01_AE and subtype B components in clade-matched vaccine strategies for Thai phase III trials. Ongoing molecular surveillance of circulating HIV-1 strains is imperative for the evaluation of HIV vaccine efficacy.

HIV-1 subtype B and CRF01_AE have been in circulation in Thailand and Southeast Asia for more than a decade. Initially separated by risk group, the two strains are increasingly intermixed, and two recombinant strains of essentially reciprocal structure have been recently reported. Here we identify additional CRF_01B recombinants and provide the evidence that HIV-1 strains now pass freely between the two high-risk populations. HIV isolates that showed discordance between CRF01_AE and subtype B in multi-region genotyping assays were selected for the study. They were drawn from 3 different cohorts in Thailand representing different risk behaviors and demographic characteristics: a drug user cohort in the north, a family planning clinic attendee cohort in the southeast, and a cohort study of the mucosal virology and immunology of HIV-1 infection in Thailand. The DNA from these isolates was PCR amplified to recover the full HIV-1 genome and subjected to sequencing and phylogenetic analysis. We establish that one particular CRF_01B recombinant, with the external envelope of subtype B and the rest of the genome from CRF01_AE, is circulating widely in Thailand. Termed CRF15_01B (also referred to as CRF15), the strain was primarily heterosexually transmitted, although injecting drug use (IDU) also played a role. In aggregate data from the studies, CRF15 constituted 1.7% of all HIV-1 infections (95% confidence interval 0.5-4.4%) and was dispersed widely in the country. The previously separate heterosexual and IDU epidemics have apparently been bridged by a new CRF. The entry of CRF15 into the mainstream of the epidemic signals new complexity in the long stable molecular picture in Thailand. These recombinants must be considered in ongoing or projected efficacy evaluations of HIV-1 vaccines and antiviral therapies.

The authors sought to determine sociodemographic and sexual and drug use risk factors for HIV infection among drug users in northern Thailand adjacent to the Golden Triangle. The authors enrolled patients admitted for inpatient drug detoxification at one treatment center in northern Thailand and studied HIV risks and prevalence using an interviewer-administered questionnaire and serum collection with HIV pretest and posttest counseling. Between February 1, 1999 and January 31, 2000, 1865 patients admitted for opiate and methamphetamine dependence completed study procedures. Overall HIV prevalence was 10.3%: 30.0% among 513 injection drug users (IDUs) and 2.8% among non-IDUs (OR = 14.8, 95% CI: 10.2, 21.6). HIV seroprevalence was 2.4% among exclusive methamphetamine users (98% of whom are non-IDUs) and 3.4% among opium smokers. Injection drug use was the dominant risk factor in multivariate models. Although Thailand is widely recognized as having a successful national response to the heterosexual HIV epidemic, seroprevalence in IDUs remains high. Despite a sharp increase of non-IDUs admitted to the drug treatment center, HIV infection and risks remained high among IDUs in northern Thailand. HIV prevention campaigns need to focus on IDUs and to implement harm reduction strategies to reduce transmission to IDUs and further contain the HIV epidemic in Thailand.