Immunological classification of poliomyelitis viruses isolated in Japan.

Poliomyelitis viruses have been immunologically grouped into three types, Brunhilde, Leon and Lansing. Although much of effort has been devoted to isolate poliomyelitis virus in Japan1-2), little is revealed concerning the immunological property of the strains isolated3). After World War II, the existence of poliomyelitis virus •gLansing•h strain in Japan was suspected from the results obtained by the neutralization test on sera of the healthy Japanese4), and furthermore, poliomyelitis virus B34 strain that was of Lansing type was successfully isolated from the stool of one healthy member of a polio patient's family, by means of mouse passage of the specimen5). At that time monkeys were not used to isolate the causative agent of the disease because they were not easily available. An epidemic of poliomyelitis has occurred in the northern part of Japan during 1949. A total of 501 (12.5/100,000 population) cases was reported from Hokkaido, and also 194 (18.9/100,000 population) cases from Aomori Prefecture. These figures represent only paralytic cases, since in Japan non-