NATIONWIDE SURVEILLANCE OF HIV-1 PREVALENCE AND SUBTYPE IN YOUNG THAIMEN

As part of routine surveillance, an HIV-1 serosurvey of 366,074 member s of successive cohorts of young Thai men entering service with the Ro yal Thai Army (RTA) was conducted between November 1989 and November 1 995. We analyzed regional and temporal trends in HIV-1 seroprevalence in young men in Thailand and determined the proportion of infections r esulting from subtypes E and B in this population in 1992 and 1995. Th e prevalence in 1992 was compared with that in 1995 by region and demo graphic group. The HIV-1 subtype was determined in a random sample of HIV-l-positive specimens in 1992 and 1995 using a V3 peptide enzyme im munoassay. From a peak of 3.7% in 1993, overall seroprevalence decline d to 3.0% in 1994 and further in 1995 to 2.5%. Between 1992 and 1995, the absolute decrease in seroprevalence was greatest in the upper Nort h (from 12.5% to 5.3%), where the prevalence has been the highest. Ove rall, 96.9% and 95.9% of typable specimens were determined to be subty pe E in 1992 and 1995, respectively. Decline in HIV-1 seroprevalence a mong young men in Thailand has continued, which suggests that HIV cont rol programs in Thailand may have been successful in decreasing spread of HIV-1. Almost all HIV-1 infections resulted from subtype E.