Abstract
Three cases of paralytic disease associated with poliovirus infection were reported. One patient had not received poliovirus vaccine nor had any contact with an individual who had received vaccine. Poliovirus type 1 was isolated from feces of this patient, and virologic studies revealed that this strain was probably a wild-type. Two patients had received the trivalent oral poliomyelitis vaccine before onset of illness. No virus was isolated from one patient, but neutralizing antibody titers against three types of polioviruses were risen. Poliovirus type 2 was isolated from feces of the other patient, and this strain was found to be vaccine-like. The fact that there is wildtype of poliovirus in spite of mass immunization against poliomyelitis, indicates the possiblity of outbreak of poliomyelitis when immunization rate falls under critical level.
