THE INCIDENCE OF HIV-1 INFECTIONS IN VILLAGE POPULATIONS OF NORTHERN THAILAND

Objectives: To determine the age- and sex-specific prevalence of HIV-1 infection in a general ambulatory population in northern Thailand in 1990 and 1992, and the incidence of HIV-1 infections between 1990 and 1992. Design: Health fairs were held in five villages in Chiang Mai pr ovince in northern Thailand between December 1989 and January 1990 and again in January 1992. Participation of all village residents was enc ouraged. Villagers were offered testing for serological markers of hep atitis B virus (HBV) infection and free HBV vaccine was made available to susceptible individuals. Methods: Sera from the two surveys were l inked and coded by demographic characteristics (age group and sex). In dividual identifiers were removed and the sera tested for HIV-1 antibo dies by enzyme-linked immunosorbent assay with Western blot confirmati on. Results: In 1990, 21 out of 1161 (1.8%) individuals were HIV-1-ser opositive; the infection rates were 3.3% in men and 0.5% in women. In 1992, 44 out of 956 (4.6%) individuals were HIV-1-seropositive. Among people included in both surveys the 2-year incidence was 2.0% in women and 4.1% in men (annual incidence, 1.0 and 2.05%, respectively); howe ver, among men over the age of 14 years the 2-year incidence was 6.3%, whereas among women of this age the 2-year incidence was 1.8% (annual incidence, 3.15 and 0.9%, respectively). Among men, incident HIV-1 in fections were common, even among those aged 50 years or more. Conclusi ons: Infections with HIV-1 are disturbingly frequent and increasing am ong adult populations in semi-rural areas of northern Thailand. In ord er to contain further spread of the epidemic public-health strategies targeted to the general public, including those in rural areas, will b e needed.