AN EPIDEMIC OF NEW INFLUENZA VIRUS TYPE B IN GUNMA PREFECTURE, 1973

An epidemic of the upper respiratory infection diseases was observed among primary schoolchildren and junior high schoolboys in Gunma Prefecture from April to July in 1973. To explore the nature of the epidemic, virological and serological examination were carried out with the materials derived from sample patients. The results is sammerized as follow :1. Influenza virus was isolated from 31 cases out of 81 materials (throat swabs). All of the isolated strains was indicated Influenza virus type B.2. A fourhold or greater rise to the titer of hemagglutination inhibiting antiboby against new influenza virus type B was recognized in 32 cases out of 56 paired sera obtained from the patients.3. All of the isolated strains was found a new influenza viruses which had been varied a significant antigenic composition than to any of the former strains.4. The study of the distribution in the population of general healthy inhabitants in Gunma Prefecture of antibody detected by the H I-test before the epidemic was found an increase in number of positive titres in age of group 31-40.