On the Geographical Distribution of Japanese B Encephalitis in the Far East Asia

Japanese B encephalitis (JBE) seemed to be known in the another name of disease in Japan about one thousand and two hundreds years ago (Kakinuma1) and Mitamura2)), however, attension was paid first by the Japanese workers, who published their views on clinical and experimental findings of it, since Economo had described an encephalitis lethargica in Europe in 1917.In 1933 the Third Sub-Committee of Encephalitis was organized in the Japanese Association for Promoting Science and Prof. Dr. R. Inada was appointed a chief of the Sub-Committee and the systematical study on a large scale has started. All the members of the Sub-Committee and the others who did not belong to the Sub-Committee have done their utmost to remove the misterious veil covering JBE. In the summer of 1933 an epidemic of JBE occured in Japan. Hayashi, 3) Okayama Medical College, was successful experimentally to transfer the disease to monkey in the same year. On the occasion of the next epidemic which took place in. 1935, many workers were able to isolate the JBE virus in Eukuoka, Okayama, Hyogo, Osaka, Kyoto, Niigata and Tokyo by using mice in the same manner of Webster in St. Louis encephalitis (SLE) in 1933. Kawamura4), Mitamura5) and Takagi6) have accordingly made clear the fact that the disease was immunologically different from the other known encephalitiden. Mitamura2) pointed out that those 30 newly isolated virus strains were almost the same though some minor variant might be found in their antigenic structure among them, and that there was one kind of JBE virus in Japan.The studies on the intensity and the frequency of distribution of the virus in various districts in the Ear East are, not only of scientific significance but also of importance for the preventive medicine. The indicators as to presume the geographical distribution of the disease are, first by the isolation of the causative agent from the host in areas, second by the positivity rate of neutralizing antibody against the virus in human and animal sera collected in such areas where the disease is reported or not and third by the report of the cases in such areas of which the clinical findings are similar to those of JBE.The positive isolation of the virus indicates an actual existence of the disease, however, it is not always successful because of troubles in the technic and the material inspite of a case confirmed serologically while the approvement of the neutralizing antibody gives a reliable suggestion to presume the geographical distribution of the virus because the technique is simple and the reaction in general specific even if it has been known that there is some nonspecific virulicidal substance in some sera. The case report is not always a liable indicator if it is confirmed by neither serological tests nor autopsy findings.Takenouchi7), Takagi9) and Mitamura9) have presumed, through the results observed in the neutralization test, that the disease is spread but very rarely, if not at all, in the district of Hokkaido till 1938. But a few cases of JBE virus was isolated by Hayashi, Mitamura and others10) from the brain of a human case. As for other areas in the Far East Asia the virus was also isolated by Kobayashi11) in Formosa in 1938, by Smorodin-tseff12) in the Maritime Province in 1938-39 where the Autumn encephalitis which is called by Rusian workers and is known to be immunologically similary to Japanese B encephalitis occurred in the same years, by Yen13) in North Chinaa in 1941, by Sabin in Okinawa in 1945 and by the same author and his colleagues in Koreas15) in the following year, 1946.