There occurred an epidemic of febrile disease among the inhabitants of Makimoto Village in Fukushima Prefecture from the 1st May, 1954. It was followed by a similar one in Ozato Village. Epidemics of the same type became also prevalent in the middle of May among the school boys of Sukagawa First Junior High School and Iwase Junior High School. At the former 340 out of 1, 100 boys, and at the latter 41 out of 276, were infected. The present report includes clinical symptoms and serological reactions examined on 100 boys of the two schools.
1) The patients had headache, fever, cough, sputum, lassitude and rhinitis. Furthermore, most of them were accompanied by severe nosebleed.
2) On the whole, there was hardly any objective sign, which could characterize the disease Leukocyte count showed normal or slightly reduced values. Moderate lymphocytosis was confirmed throughout the course of disease. Remarkable shift of leukocyte nuclei to the left was observed at the early stage. Plasma cells did not appear in hemogram.
3) By the hemagglutination inhibition test with Influenza virus types A (PR, 8 strains), A'(Kojiya, 2 strains) and B (Tokyo, 1-52, 4 strains), the epidemic was identi fled as one due to Influenza virus B.
4) The disease was extremely contagious among the school boys. it could be brought to subside at the Sukagawa First Junior High School only when the school was closed for 8 days. No serious infection was experienced, which might endanger the patient.
