Abstract
Polioviruses of various types isolated in Hokkaido from paralytic poliomyelitis patients, familial contacts and healthy children at epidemic and non-epidemic periods during the 5 years from 1956 to 1960 were tested for the reproductive capacity at 40°C; (rct/40). The relationship between the rct/40 character of the viruses and their sources of isolation was investigated from epidemiological viewpoint.
1) All the type 1 polioviruses isolated at non-epidemic and pre-epidemic periods were the characters of either rct/40± or rct/40- regardless of the source of virus isolates. With the progress of the 196 epidemic, however, the virus of rct/40- disappeared while that of rct/40+ increased rapidly in the number.
2) All the type 1 viruses obtained from feces and the CNS of fatal cases at the acme of the epidemic were highly positive in the character. However, the rct/40 characters of viruses from both the paralytic cases and familial contacts were not always the same.
3) The type 2 polioviruses isolated from paralytic cases at the sporadic were mostly rct/40+ while those of the same type from healthy children were invariably rct/40±. In contrast, most of the type 3 polioviruses isolated from paralytic cases at the sporadic showed greater EOG than that of the type 3 Sabin strain at the temperatures over 40°C.
