STUDY OF JAPANESE ENCEPHALITIS VIRUS IN CHIANGMAI VALLEY, THAILAND VI. SUMMARY AND CONCLUSIONS1

Abstract

Grossman, RA (Department of Epidemiology, U.S. Army Medical Component SEATO, APO San Francisco, California 96346), R. Edelman and D. J. Gould. Study of Japanese Encephalitis in Chiangmai Valley, Thailand. VI. Summary and conclusions. Am J Epidemiol 100:69–76, 1974.—This final paper in a six-paper series summarizes the temporal interaction of the important variables of Japanese encephalitis virus (JEV) epidemiology in the Chiangmai Valley in northern Thailand. Further evidence is presented for the conclusion that JEV transmission to pigs and humans is endemic and occurs throughout the year and that JE epidemics are directly related to increased transmission during the rainy season months. The Chiangmai Valley, with its semitropical climate, apparently shares the epidemiologic patterns of JEV transmission in the epidemic (temperate) and endemic (tropical) JE zones. Evidence is presented suggesting that persons under age 20 who have had prior dengue infections are sometimes protected against the development of Japanese encephalitis; however the proportion protected is probably not large. Analyzing the data without regard to prior dengue exposure reveals that one- to nine-year-olds and 10- to 19-year-olds both produce one JE case for every 300 inapparent JEV infections.