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目的:分析济宁市2017—2020年度乙型流感病毒血凝素(HA)和神经氨酸酶(NA)基因变异情况及分子进化特征。方法:采集2017—2020年度济宁市哨点医院和流感暴发疫情病例咽拭子标本，进行核酸检测、病毒分离，选取20株乙型流感病毒代表毒株进行n HA和n NA基因测序，利用生物信息学软件构建进化树并分析分子进化特征。n 结果:2017—2020年度共监测病例标本4 575例，流感病毒阳性842例，其中乙型流感病毒阳性398例，阳性率8.70%(398/4 575)，占比47.27%(398/842)。2017—2020年度济宁分离的BV系和BY系流感病毒与疫苗株比，n HA基因同源性分别为98.7%～98.8%、98.5%～99.1%。2018—2020年度BV系流感归属于Victoria clade 1A分支，2017—2018年度BY系流感归属于Yamagata clade 3分支。对抗原表位和耐药位点的变异情况进行了分析，发现多处抗原表位发生了变异，但未发现神经氨酸酶抑制剂耐药位点的变异。n 结论:2017—2020年度济宁市BV系和BY系乙型流感病毒均发生了数个抗原位点变异，出现了抗原转变，可能是引起乙型流感暴发的原因。“,”Objective:To analyze the variation and evolution characteristics of hemagglutinin (HA) and neuraminidase (NA) genes of influenza B virus circulating in Jining from 2017 to 2020.Methods:Throat swab specimens were collected from patients with influenza-like symptoms in sentinel hospitals and influenza outbreaks in Jining from 2017 to 2020 and tested for influenza B virus nucleic acid. After virus isolation, 20 representative strains of influenza B virus were selected to sequence the full length of n HA and n NA genes. Phylogenetic trees were constructed and the molecular characteristics were analyzed using bioinformatics software.n Results:A total of 4 575 specimens were collected and 842 of them were positive for influenza virus, including 398 (8.7%, 398/4 575) influenza B virus-positive specimens. The positive rate of influenza B virus was 47.27% (398/842). The isolated influenza B virus strains of Victoria (BV) and Yamagata (BY) lineages from 2017 to 2020 shared 98.7%-98.8% and 98.5%-99.1% homology in n HA gene with vaccine strains, respectively. The BV lineage strains isolated from 2018 to 2020 belonged to Victoria clade 1A branch and the BY lineage strains isolated from 2017 to 2018 belonged to Yamagata clade 3 branch. Mutations were detected in several antigenic sites, but not in the sites related to NA inhibitor resistance.n Conclusions:Mutations in several antigenic sites caused antigenic changes in influenza B virus of BV and BY lineages, which might be related to the outbreaks of influenza B virus infection in Jining during 2017 to 2020.