Identification and transmission risk assessment of type Ⅰ vaccine-derived poliovirus in Anhui Province in 2023
Objective To analyze the genotypes and characteristics of two vaccine-derived poliovirus(VDPV)strains isola-ted from a non-acute flaccid paralysis(non-AFP)case in Anhui Province in 2023,and to explore the influence of this case on maintaining polio-free status in Anhui province.Methods Poliovirus(PV)was isolated from two samples of a non-AFP case in Anhui Province in 2023.The PV was identified by real time fluorescent quantitative RT-PCR.The single type strain was obtained by neutralization experiment,the viral RNA was extracted and amplified by RT-PCR,and the nucleotide se-quence of VP1 region was determined and analyzed.Results Two mixed type Ⅰ+Ⅲ PV strains were isolated from the doub-le fecal samples of the non-AFP case.Type Ⅰ(2023MYKJH 01-1 and 2023MYKJH 01-2)had 13 and 12 nucleotide vari-ants,with variation rates of 1.4％and 1.3％,respectively,they were identified as type Ⅰ VDPV and in a different branch from the type Ⅰ VDPV detected in other province in China in recent years.Type Ⅲ were vaccine-like strains.Type Ⅰ VDPV was not isolated from subsequent stool samples.Conclusion One non-AFP case of two type Ⅰ VDPV strains detected in Anhui Province in 2023 did not undergo continuous detoxification,resulting in a lower risk of developing type Ⅰ VDPV circu-lation.
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