[Analysis of genetic characteristics of type II non-wild poliovirus in mainland China, 2010].

To study the genetic characteristics of 123 type II non-wild polioviruses isolated from acute flaccid paralysis (AFP) cases in mainland China in 2010, provide the scientific basis for maintaining the "polio-free" status, and the switching use of polio vaccine for China. VP1 gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) and the PCR products were then sequenced. The sequence results were analyzed with Sequencher 4.8, BioEdit 7.0.9 and MEGA 5.0. Of 65 strains, nt2909 was found to be a mutation hotspot, and also a neurovirulence determinant in VP1 region. During 2010, two vaccine-derived polioviruses (VDPVs) were isolated from Yunnan province, China and no wild poliovirus (WPV) was isolated. The epidemiological studies and laboratory results of the two VDPVs showed that they were newly discovered VDPVs because of the genetic difference from other VDPVs strains isolated in the world, implying the sensitive poliovirus surveillance network could timely detect the transmission of VDPVs and the importation of WPV.