ENCEPHALITIS

Abstract

From studies made on the encephalitides in the United States and Canada during the last decade, the evidence favors setting apart from the many types a group of virus infections which appear to be arthropod borne. These infections have come to be known as western equine and eastern equine encephalomyelitis and St. Louis encephalitis. Now, however, they are recognized to be no longer limited geographically to east and west or in host range to horse and man. Epidemiologically and clinically they are closely related. It would seem reasonable, therefore, to classify them as members of an increasingly large group of diseases which might well be called arthropod borne virus encephalitides and to consider and study them together. In this paper the extensive epidemiologic studies made during the summer of 1941 in the relatively isolated Yakima Valley, Washington, will be summarized briefly. These studies were of a broad nature, planned in