昆明市2018—2021年手足口病病例中柯萨奇病毒A组4型流行情况及VP1编码序列基因特征分析

Prevalence of coxsackievirus A4 among patients with hand, foot, and mouth disease in Kunming in 2018—2021 and the phylogenetic analysis of its VP1 coding gene sequence

目的 分析昆明市2018—2021年手足口病病原构成,研究柯萨奇病毒A组4型(coxsackievirus A4,CVA4)的流行特点及VP1编码序列系统进化与氨基酸变异情况。方法 采用实时荧光逆转录聚合酶链反应(real-time reverse transcript-polymerase chain reaction, real time RT-PCR)对2018—2021年昆明市疾病预防控制中心监测到的昆明市手足口病病例标本3 553份进行肠道病毒核酸检测,描述CVA4的流行情况,并进行VP1编码序列全长测序、氨基酸位点变异及系统进化分析。结果 共检出肠道病毒阳性标本2 531份,阳性率71.24%,其中CVA16、EV-A71及其他肠道病毒(非EV-A71、非CVA16)占阳性样本的构成比分别为38.05%(963/2 531)、4.11%(104/2 531)和57.84%(1 464/2 531)。CVA4阳性52份,其高发区域为昆明市区及东南部,涉及5个县区,阳性数占CVA4病例总数的73.08%(38/52),高发时间为8—12月,占CVA4病例总数的71.15%(37/52),高危人群为1~3岁儿童,占86.54%(45/52),男性多于女性,多引起轻症。CVA4共测序成功51份,核苷酸相似性为90.90%~100.00%,氨基酸相似性为97.30%~100.00%,均为C基因型C2亚型,分为3个传播链(cluster),clusterⅠ以2019年昆明市毒株为主,clusterⅡ以2020和2021年昆明市毒株为主,clusterⅠ、Ⅱ包含了98.04%(50/51)昆明市毒株。与原型株High Point(AF081295)VP1区氨基酸序列相比,有R18K、T23V、A34T、S102A、A200T、I262V、R274K和Y285H共8个高频氨基酸变异位点。结论 2018—2021年昆明市手足口病病原谱中其他肠道病毒(非EV-A71、非CVA16)占主导地位,CVA4作为其中的一个重要类型,属于C2亚型。应针对昆明市主城区及东南部区县、8—12月和1~3岁儿童等因素合理配置防控资源,做好CVA4防控工作。

Objective To discuss the etiology of hand, foot, and mouth disease(HFMD) in Kunming from 2018 to 2021, and to understand the epidemiological and the phylogenetic characteristics and amino acid variation of the VP1 coding gene of coxsackievirus A4(CVA4). Methods Enterovirus RNA was characterized by real-time reverse transcript-polymerase chain reaction(real-time RT-PCR) among 3 553 samples were sequenced,amino acid variation and phylogenetic characteristics were analyzed. Results A total of 2 531samples were enterovirus positive with the overall positive rate of 71.24%(2 531/3 553).The positive rate was 38.05%(963/2 531)for CVA16,4.11%(104/2 531)for EV-A71and 57.84%(1 464/2 531)for other enterovirus.Fifty-two cases were CVA4positive,and 73.08%(38/52)were from urban areas and southeastern areas of Kunming.The number of cases peaked during August and December,accounting for 71.15%(37/52).Children of 1-3years old with more boys than girls accounted for 86.54%(45/52)of cases and majority were mild cases.VP1coding genes were successfully sequenced in 51samples with the nucleotide(nt)similarities of 90.90%-100.00% and the amino acid(aa)homologies of 97.30%-100.00%,they were all C2sub-genotype.Phylogenic analysis showed 3clusters.ClusterⅠ was dominated by2019Kunming strains and cluster Ⅱ was dominated by both 2020and 2021 Kunming strains,these two clusters contained 98.04%(50/51)of Kunming strains.Compared with the prototype strain High Point(AF081295),8amino acid variation sites(R18K,T23V,A34T,S102A,A200T,I262V,R274K and Y285H)in VP1coding sequence were identified. Conclusions From 2018to 2021,the leading pathogens of HFMD circulating in Kunming are non-EV-A71and non-CVA16enteroviruses,and CVA4,as an important type of pathogen,belongs to the C2sub-genotype.Most CVA4related HFMD cases are from urban areas of Kunming and the south-eastern areas,case number peaks from August to December and children aged 1-3year old are more vulnerable to CVA4 infection.