A LONGITUDINAL STUDY OF ENTEROVIRUS INFECTIONS IN KAWASAKI, JAPAN

A longitudinal study of enteric virus infections in children under six years in kindergartens and day nurseries has been conducted since 1962 in an area of Kawasaki City. Results of virus isolation during a five years study are summarized as follows; (1) Out of a total of 2500 fecal specimens 397 were proved to contain at least one viral agent. Thirty-three polioviruses, 164 coxsackieviruses group A, 49 coxsackieviruses group B, 109 echoviruses, 11 adenoviruses and 13 reoviruses were identified, while 35 isolates remained unidentified. Dual infections were found only in 17 specimens, of which 5 were mixed infection of two types of polioviruses and one was mixed infection of poliovirus and coxsackievirus group A type 4. (2) Poliovirus isolations were presumably related to the strains derived from live oral poliovaccine. (3) The rate of enterovirus isolation was high in summer and low in winter. (4) The isolation rate was highest in younger age groups and declined with age progress. (5) Approximately 10 to 12 different serotypes with a few dominant types were isolated every year. (6) The isolated enteroviruses were grouped according to the grade in endemicity as expressed by the length of year-intervals for reappearance.