Effect of climatic factors and population density on varicella zoster virus epidemiology within a tropical country

Blood samples were collected from healthy subjects, aged 9 months-29 years in urban and rural communities from 4 distinct regions in Thailand, to dete rmine the seroprevalence rate of varicella-zoster virus (VZV) antibody and its relationship with demographic, climatic, and socioeconomic factors. The overall seroprevalence rate was 52.8% and increased from 15.5% in the 9-mo nth to 4-year-old group to 75.9% in the 20-29 year-olds. The age adjusted s eroprevalence was significantly higher in the cooler than in the warmer reg ions. In the warmer regions only, the age-specific seroprevalence was signi ficantly higher in the urban population than in the rural population. In Th ailand, climate is the main determinant of VZV seroprevalence. The delayed onset of natural immunity is more marked in warmer climate areas. Populatio n density is a secondary determinant; in the warmer areas, the pattern of a dolescent and adult susceptibility was greater in rural than in urban areas .