title: Geographic dynamics of viral encephalitis in Thailand.
abstract: Viral encephalitis (VE) continues to be a major disease in Asia, causing serious illness which may result in death or have neurological sequelae. This study involves an ecological analysis of the climatic, geographic and seasonal patterns of clinically reported VE in Thailand from 1993 to 1998 to investigate regional and seasonal differences in disease incidence. Three thousand eight hundred and twenty nine cases of VE were clinically diagnosed nationwide during the study period by the Thai Ministry of Public Health. Spearman rank correlations of temporal, spatial and geographic variables with disease incidence were performed. The monthly incidence of VE correlated significantly with seasonal changes in temperature, relative humidity and rainfall in the north-northeast region of Thailand (P < 0.001), whereas incidence in the south-central region correlated only with relative humidity (P = 0.003). Spatial analysis revealed a positive correlation of disease with elevation (P < 0.001), and negative correlations with rice-field cover (P < 0.001), agricultural land-use (P < 0.001) and temperature (P = 0.004) in the north-northeast region. No significant spatial correlation was identified in the south-central region. The spatial distribution of VE suggests that etiologic variations may be responsible, in part, for the geographic patterns of disease. Active etiologic surveillance is necessary in a variety of geographic settings in order to provide physicians with information necessary for disease prevention and clinical management.
authors.affiliation: Yale University School of Medicine, 367 Cedar Street, New Haven, CT 06510, USA. timothy.henrich@yale.edu
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Henrich
authors.forename: Sombat
authors.initials: S
authors.lastname: Hutchaleelaha
authors.forename: Vitaya
authors.initials: V
authors.lastname: Jiwariyavej
authors.forename: Philippe
authors.initials: P
authors.lastname: Barbazan
authors.forename: Narong
authors.initials: N
authors.lastname: Nitatpattana
authors.forename: Sutee
authors.initials: S
authors.lastname: Yoksan
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Gonzalez
mesh_terms: D017677:Age Distribution; D015331:Cohort Studies; D018792:Encephalitis, Viral / Q000175:diagnosis / Q000453:epidemiology*; D006801:Humans; D012621:Seasons; D013785:Thailand / Q000453:epidemiology; D014329:Tropical Climate