An outbreak of mild illness, affecting mainly school children, occured in Gunma Prefecture during the lates summer of 1958.
Evidence then available indicated that the illness represented a clinical entity different from the more commonly known respiratory diseases.
By usual laboratory examinations, in eluding HeLa cell cultures, no causative agent was found in specimens from the patients with fever. Isolations from the throat washing and the feces of the patients by means of the hemadsorption technic and monkey kidney tissue culture were unsuccessful. In serological tests, no antibody increase was found for any prototype strains of influenza, mumps, parainfluenza, and adenoviruses.
