Virological monitoring and analysis of polioviruses in Qinghai 2017

Objective To evaluate 2017 poliovirus surveillance in Qinghai Province. Methods According to the World Health Organization (WHO) 4 th edition of the polio laboratory manual procedure for virus isolation, the isolated L20B positive strain was identified as intratypic differentiation (ITD) by the China Center for Disease Control and Prevention, CDC). The National Polio Laboratory performed the nucleotide sequence determination of the capsid protein VP1 coding region of poliovirus (PV) and analyzed the poliovirus surveillance and the result of analysis of the cases with acute flaccid paralysis (AFP) reported in Qinghai Province in 2017 and stool samples of healthy children. Results In 2017, Qinghai CDC Polio Laboratory received specimens of 211 AFP cases and healthy stool samples. PV2 strains were isolated with a separation rate of 0.95%. Non-polio enterovirus (NPEV) strains were isolated from 25 strains with the isolation rate of 11.85%. Two PVs were used for ITD. All of them were vaccine-associated strains. Conclusions In 2017, the Qinghai CDC Polio Laboratory did not find any poliovirus and vaccine-derived poliovirus in the AFP cases and stool samples from healthy persons, maintaining the polio-free status. Key words: Acute flaccid paralysis; Poliovirus; Virological monitoring