Seroepidemiological Studies on Prevalence of a New B Type Influenza Virus (B/Yamagata/1/73 strain)

Abstract

For revealing the practical state and the epidemiological picture of influenza B, which invaded and infected in Japan from April 1973 to the early stage of 1974, it was studied seroepidemiologically and the following results were obtained. 1. B/Yamagata/1/73 strain which was isolated and identified in the present infection had some antigen common to typical B type strain which had been isolated in the past. 2. The HI antibody against B/Yamagata/1/73 strain observed in the sera of adults before the infection, but was not found in the sera of persons younger than high-school students. 3. The HI antibody increased to about 32 to 256-folds after the infection by B/Yamagata/1/73 strain. 4. After the infection by B/Yamagata/1/73 strain, the HI antibodies against B/Tokyo/7/66 strain and B/Kanagawa/1/73 strain were found to increase considerably. 5. Among the subject who had the HI antibody values against B/Yamagata/1/73 strain more than 32-folds in the sera after the infection, about 87% had CF(S) antibody, 6. By reducing slightly the amount of the attacking virus from a usually used one, a neutralizing antibody against B/Yamagata/1/73 strain was detected from the sera having high HI antibody against B/Tokyo/7/66 strain, though the HI antibody value against B/Yamagata/1/73 strain was less than 16-folds. 7. The number of the patients were greatly varied among the school and the classes attacked by the infection of B/Yamagata/1/73 strain. The difference of the patient numbers seemed to have some reaction to the HI antibody and the neutralizing antibody against B/Tokye/7/66 strain and B/Kanagawa/1/73 strain which were found to have some common antigen to B/Yamagata/1/73, and to their degrees in the sera before the infection.