Update on HIV/AIDS in Thailand.

Thailand experienced its first case of AIDS in 1984. Approximately 800,000 Thais were infected with HIV in 1995 and 1 million Thais became infected by the year 2000. There have been 5 major epidemic waves: among male homosexuals (started 1984-5), intravenous drug users (started 1988), female commercial sex workers (started 1989), male clients (started 1990), and housewives and the newborn (started 1991). Approximately 96 per cent of HIV-1 infected Thais carried recombinant subtype A/E, the rest carried B'. In a male seroconvertors cohort of 235 cases, median time to show CD4 <200 cells/microL was 6.8 years. Five years survival was significantly lower than that of the other subtype B seroconvertors study, i.e., 82 per cent compared to 90 per cent. Interestingly, 13.5 per cent of seronegative Thais showed homozygous SDF1-3'A polymorphism, which suggests that approximately one-tenth of Thais may become long-term non-progressors after HIV-1 infection. Primary HIV infection syndrome is rare among Thai patients (1.1%). In contrast, it was 50-90 per cent in Western cohorts. In early symptomatic patients, one-third developed pruritic pappular eruptions (PPEs). In advanced stage, disseminated tuberculosis, Pneumocystis carinii pneumonia (PCP), cryptococcosis, and esophageal candidiasis are commonly found. In Northern Thailand, however, Penicillium marneffei infection or penicillosis is more common than cryptococcosis. The recent understanding of HIV pathogenesis suggests that HIV eradication is unlikely to be achievable with current strategies. Several National HIV treatment guidelines including the Thai guideline have been recommended treatment with triple antiretroviral regimen when patients become symptomatics or CD4+ <200. Current development of antiretroviral therapy which includes new agents, new formulas, and pharmacokinetic enhancements, is directed to better potency, higher genetic resistant barrier, less pill burden, and once a day dosing. These will ultimately improve the adherence and the long-term effectiveness of antiretroviral treatment. In reality, however, although the cost of triple regimen is dramatically declining, many patients still can not afford it. Primary prophylaxis and early diagnosis and treatment of opportunistic infection should be considered in patients with CD4+ <200 cells/microL. Modified short course ZDV studies and donation campaigns for preventing mother-to-child transmission, clinical trials to investigate the best use of expensive anti HIV medications in a poor resource setting have been or are being conducted. Nine phase I/II HIV-1 vaccine trial protocols have been or are being tested. A phase III trial of gp120 subtype B/E (AIDSVAX, VaxGen) was started in 1999, a total of 2,500 volunteers will be enrolled, and interim analysis is planned for August 2002. Thai investigators are also participating in pre-clinical development of recombinant BCG and DNA vaccines. Multidisciplinary and multi-level approaches, both by the government and private sectors, have had a positive impact on the HIV epidemic as shown by the declining seroprevalence of HIV infection in Thai male conscripts, and of major sexually transmitted diseases in men. Nevertheless, more effort at the grass roots level is needed to ensure further success and sustainability of the control of the HIV epidemic in Thailand.