2015-2019年北京市麻疹病毒分子流行病学分析

Molecular epidemiological analysis of measles virus in Beijing from 2015 to 2019

目的分析2015-2019年北京市麻疹病毒(measles virus,MV)分子流行病学特征,为消除麻疹提供实验室依据。方法通过北京市麻疹实验室网络收集2015-2019年麻疹病毒阳性咽拭子标本,提取病毒核酸后采用逆转录聚合酶链反应(RT-PCR)方法扩增麻疹病毒N基因C末端450个核苷酸片段,对扩增产物进行核苷酸序列测定,获得基因序列同WHO麻疹病毒基因型代表株、中国和其他国家D8基因型参考株构建系统进化树,分析核苷酸和氨基酸同源性;对D8和B3基因型麻疹病例进行描述性分析。结果2015-2019年全市麻疹病毒基因型鉴定株546株,其中H1a基因型531株,疫苗株5株,B3基因型1株,D8基因型9株,其中8株为2019年流行株。本土株H1a基因型MV核苷酸和氨基酸同源性为91.5%~100.0%和73.6%~100.0%。2019年8例D8基因型麻疹病例均为成人,其中2例为一起暴发疫情,其余6例为散发病例。结论输入性D8基因型成为2019年北京市MV主要流行基因型;2015-2019年随着麻疹发病下降,本土基因型H1a已经不占优势,而其他不同基因型输入,形成混合流行的趋势,建议在消除麻疹工作中,不仅要努力阻断本土麻疹病毒传播,更要防控非本土基因型病毒输入和持续传播,避免其逐渐演化为优势毒株而建立本土传播的风险。

Objective To analyze the molecular epidemiological characteristics of measles virus(MV)in Beijing from 2015 to 2019,and to provide laboratory basis for measles elimination.Methods Measles virus-positive throat swab samples were collected through the Beijing Measles Laboratory network from 2015 to 2019.After the viral nucleic acid was extracted,450 nucleotide fragments of the C terminal of the N gene of MV were amplified by RT-PCR.Nucleotide sequencing was performed for the amplified products.The phylogenetic tree was constructed with the representative strains of WHO measles virus genotype D8 genotype reference strains in China and other countries.Genotype identification was conducted and the nucleotide and amino acid homology analysis was carried out.A descriptive analysis of measles cases with D8 and B3 genotypes was conducted.Results From 2015 to 2019,the genotypes of 546 MV were identified in the city,including 531 of H1a genotype,five vaccine strains,one of B3 genotype,and nine of D8 genotype,among which eight were epidemic strains in 2019.The homology of indigenous H1a genotype MV nucleotide and amino acid was 91.5%-100.0% and 73.6%-100.0%.In 2019,all eight cases of D8 genotype measles were adults,with two being an outbreak and the remaining six sporadic cases.Conclusions The imported D8 genotype had become the main MV genotype in Beijing in 2019.With the decrease of measles incidence in 2019,native genotype H1a was no longer dominant,while other different genotypes were imported,forming a mixed epidemic trend.It was suggested that in the elimination of measles in Beijing,efforts should be made not only to block the transmission of local measles virus,but also to prevent and control the import and continuous transmission of non-local genotype virus,so as to avoid the risk of establishing local transmission by gradually evolving into a dominant strain.