Genetic analysis of wild-type 1 poliovirus isolates in China, 1985-1993.

We examined the genomic variability of 26 wild-type 1 polioviruses isolated from 12 provinces in China from 1985-1993. The poliovirus genome region that encodes the N-terminal portion of the VP1 protein was amplified by the polymerase chain reaction (PCR). The PCR product of each isolate was analysed by restriction fragment length polymorphism (PCR-RFLP) and by direct sequencing. Several groups of viruses with different PCR-RFLP patterns were found to cause outbreaks in China during this period. Viruses with identical PCR-RFLP profiles were dominantly isolated in 11 provinces from 1991 to 1993 and were considered to be the major epidemic strain in China. On the other hand, in the GuangDong province, a different group was responsible for each year's outbreak, while in the XinJiang autonomous prefecture, a single strain was consistently isolated from 1990 to 1993. Understanding of the nationwide distribution of wild poliovirus is very important for interrupting its transmission during the final stage of the eradication program in China.