AEGiS-13IAC: Sustained low HIV-1 incidence among cohorts of young northern Thai adults: Confirmation of Thailand's success in HIV prevention.

13th International AIDS Conference

Durban, South Africa - July 9-July 14, 2000

Sustained low HIV-1 incidence among cohorts of young northern Thai adults: Confirmation of Thailand's success in HIV prevention.

Int Conf AIDS 2000 Jul 9-14; 13:(abstract no. ThOrC671)

Khamboonruang C, Natpratan P, Borwornsin S, Cegielski P, Srirak N, McNeil J, Renzullo P, Benenson M, Beyrer C
C. Khamboonruang, PO Box 80 CMU, Chiang Mai 50202, Thailand, Tel.: +66 53 221 966, Fax: +66 53 221 849, E-mail: rvtu@chm.cscoms.com

BACKGROUND: To measure HIV-1 incidence in preparation for community based HIV vaccine trials in northern Thailand, we identified and followed two large community cohorts comprising adult residents in districts with know high HIV-1 prevalence around Chiang Mai City.

METHODS: Peri-urban communities were selected that had known high HIV-1 prevalence and low mobility. From 1998-1999, two cohorts (A = 2274 and B = 2259) of adults aged 20-45 (A) and 20-35 years (B) were offered enrolment in sero-incidence studies of six months duration each. After informed consent and pre-test counselling, subjects had a blood draw for HIV-1 serology, syphilis, and completed a brief self-administered questionnaire. They were counselled 2 weeks later, and the process was repeated at 6 months.

RESULTS: Retention over 6 months was high in both cohorts, a total of 4266 of 4533 (94.1%) completed the study. Baseline HIV prevalence was 2.1% in cohort A and 2.9% in cohort B. Prevalence in cohort B was higher among men 4.3% (40/932) than among women 1.9% (25/1327), p>.001. In cohort A we identified two incident infections, for an annualised HIV incidence of 0.18/100PY. In cohort B, completed in December 1999, there were no incident infections detected. Summing person years across cohorts, we estimate a community HIV-1 seroincidence of less than 0.1/100PY during 1998-1999.

CONCLUSIONS: Northern Thailand had a severe epidemic of HIV-1 in the early 1990's, followed by vigorous multi-sectorial prevention efforts. While data including declining STD rates, declining HIV-1 prevalence from sentinel surveillance, and incidence declines in selected populations (military recruits and STD patients) have suggested the northern Thai epidemic could be slowing, our findings confirm a dramatic decrease in HIV spread in a large community-based sample. The Thai response to the HIV epidemic is evidence of the possibility of achieving control of HIV infection, even in resource limited settings.

Keywords: AEGIS, Incidence, HIV-1, HIV Infections, Prevalence, Thailand, AIDS Vaccines, HIV Seropositivity, Syphilis, Cohort Studies, Disease Outbreaks, Military Personnel, Adult, Human, Female, Male, prevention & control, epidemiology
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