Japanese B encephalitis; a complete review of experience on Okinawa 1945-1949.

Summary 1.  Complete data pertaining to studies on Japanese B encephalitis on Okinawa during the years 1945 through 1949 is presented. 2.  The occurrence of the disease in natives is examined in the light of population trends and accuracy of diagnosis. A total of 401 cases, with a case fatality of 35 per cent, have been observed during these five years. During the same period twenty-one cases have occurred in Americans, with a case fatality of 28 per cent. 3.  Laboratory aspects of the disease are presented with particular emphasis on time of development and persistence of antibodies. The role of “inapparent” infections is reviewed. Definite evidence is presented to validate the occurrence of such infections. 4.  The serologic response to vaccination is demonstrated. The number of cases in vaccinated Americans is not sufficient to permit deductions as to the protective value. The response to recall vaccination is greater than the initial response. The use of vaccine with the subsequent recall serological response as a survey tool is outlined. 5.  The serological pattern in various animals suggests that practically all mammals are or have been infected. Potential arthropod vectors are reviewed, and the thus-far futile efforts to prove vector are summated. 6.  Areas for future study are delineated.