MOLECULAR EPIDEMIOLOGY OF POLIOVIRUS IN CHINAIN THE EPIDEMIC PERIOD OF 1989-1994

oliomyelitis was epidemic during 1989- 1994 in mainland China. Heavy outbreaks werelocated in the east, middle and south of China. Nearly 100 isolates from 18 provinces duringthis period were analyzed for their molecular characteristics. It was found that wild polio typeI was the major agent of polio epidemic in China. Although there was no wild type 2poliovirus found, type 3 wild poliovirus was isolated in Xingjiang province in 1993, inaddition to type 1 wild poliovirus circulating there for years. An type 1 wild poliovirusesclustered into 4 genotypes by sequence analysis: CHNP1-JX89, CHNP1-R91,CHNP1-GX90 and CHNP1-XJ90. The CHNP1 -R91 genotype included all recombinantviruses whose ancestor arose in the north of China in 1991. Further analysis by nucleic acidsequencing proved that Sabin 1 vaccine virus was involved in this eveat in which a vaccinevirus recombinted with one of wild polioviruses from the CHNP1-JX89 genotype group. Thewild polioviruses in CHNP1 -JX89 and CHNP1 -R91 were the main genotypes causing polioepidemics in China in the .period of 1989- 1994. This study first established the transmissionpattem of wild poliovirus and the molecular epidemiological relationship of polio viruses indefferent regions in China.