TYPE I POLIOVIRUS ISOLATED FROM THE POLIOMYELITIS PATIENTS PREVALENT IN EHIME PREFCTURE DURING THE PERIOD FROM APRIL TO JULY, 1956

Abstract

An outbreak of poliomyelitis epidemic was encountered among the children under 14 years old at the limited areas in Ehime prefecture during the period from April to July, 1956. The isolation and identification of the causative agent were undertaken from the stools collected from 55 out of 73 cases all together with non-paralytic and paralytic cases by means of the tissue culture using monkey- and HeLa cells. It is the first report of polio epidemic in Japan which was proven to be caused by the type I poliovirus only.
Nine strains were isolated from 9 out of 15 paralytic polio cases and 11 from 11 out of 40 non-paralytic cases and they were identified as type I poliovirus. The invasion of the virus there was so marked that 5 out of 7 children under 17 years old suffered from the disease in one family and all 2 children under 7 years old got the disease in another family.
In view of the preventive medicine it is of importance to note that the virus was recovered from 6 out of 14 cases on first to 10th day, from 3 out of 10 cases on 11th to 20th day, from 2 out of 6 cases on 21st to 30th day and from 6 out of 6 cases on 31st to 40th day after onset of the disease respectively. As for the amount of the virus in the stool from the patient, 10TCID₅₀ were calculated in 10 cases, 100TCID₅₀ in 5 cases and 1000TCID₅₀ in one case on the 10th day of illness and no relationship was observed between the amount of virus in the stool and the day of illness.