Objective: To evaluate trends in HIV-1 seroprevalence in Thailand. Des
ign: HIV-1 serosurvey of successive cohorts of young Thai men entering
service with the Royal Thai Army (RTA) between November 1989 and Nove
mber 1994. Methods: In November 1989, the RTA Medical Department began
routine HIV-1-antibody screening of men who were selected by lottery
for conscription. Between November 1989 and November 1994, 311 108 you
ng men were screened at induction. Demographic data were collected bet
ween November 1991 and May 1993 and again in November 1994. Results: T
he seroprevalence of HIV-1 among conscripts nationwide increased rapid
ly from 0.5% in 1989 to 3.5% in 1992 and reached 3.7% in 1993. In 1994
, the overall prevalence decreased to 3.0%. The decrease was greatest
in the upper North (from 12.4% in 1992 to 7.9% in 1994), where the pre
valence has been the highest. However, decreases were observed in men
from all regions of residence in the country, from both rural and urba
n areas, and at all educational levels. Conclusions: The decline in pr
evalence suggests declining incidence and that HIV control programs in
Thailand are having an impact on the HIV epidemic.