Ecologic Studies of Japanese Encephalitis Virus in Japan

The human epidemics of encephalitis which occur yearly in Japan during August and September are caused by a virus with a complex life cycle involving vertebrates and vector mosquitoes. During summer epidemics and epizootics, virus is readily recoverable in nature from diseased man and animals. Yet the biologic mechanisms responsible for appearance of epidemics and the exact whereabouts of virus during interepidemic periods have been poorly understood. The studies which follow represent an attempt to elucidate the mechanism by which epidemics of Japanese encephalitis (JE) occur. They were initiated in 1952 near Tokyo, Japan by U. S. Army Personnel of the 406th Medical General Laboratory and subsequently were extended into a series of 6 yearly observations of the ecology of JE virus. This introduction presents essential background information and concepts necessary to understand and interpret results of the other articles.