聊城市某小学一起水痘暴发事件调查与病原学研究

Investigation and etiological study on outbreak of varicella in a primary school in Liaocheng

目的 查明2021年10月山东省聊城市某小学水痘疫情暴发原因,分析流行病学和病原学特征。方法 采用现场流行病学调查方法收集水痘病例资料,采集部分病例疱疹液,开展水痘—带状疱疹病毒(VZV)荧光定量PCR检测,通过PCR扩增开放阅读框(ORF)ORF22、ORF38和ORF62片段,并测序分析单核苷酸多态性(SNP),确定基因型和毒株型。结果 共调查学生和教师1 600人,累计发生水痘病例14例、罹患率0.88%,均为二年级学生,疫情全程持续20 d,出现1个发病高峰,涉及2个班,未接种水痘疫苗(VarV)儿童罹患率为45.45%,接种VarV儿童罹患率为6.25%,VarV保护效果(VE)为86.25%,9份疱疹液标本VZV核酸检测结果均为阳性;ORF22、ORF38和ORF62序列中的SNP分析显示,VZV毒株均为Clade2型野毒株。结论 本次水痘暴发疫情与人群免疫水平低有关,VZV流行株是Clade2型野毒株;应深入开展健康教育活动,以提高水痘疫苗接种率。

Objective To find out the causes of the varicella outbreak in a primary school in Liaocheng city of Shandong province in October 2021, and analyze the epidemiological and pathogenic characteristics. Methods The data of varicella cases were collected through field epidemiological investigation, and the herpes fluid of some cases was collected. The varicella-zoster virus(VZV) was detected by fluorescent quantitative PCR. The open reading frame(ORF) of ORF22,ORF38, and ORF62 fragments were amplified by PCR, and the mononucleotide polymorphism(SNP) was sequenced to determine the genotype and strain type. Results A total of 1 600 students and teachers were investigated, with 14 varicella cases and incidence rate of 0.88%. All cases were the second grade students. The course of epidemic lasted for 20 days, with one peak of incidence and 2 classes were involved. The incidence rate of varicella was 45.45% in the children who did not receive the varicella vaccine(VarV), and was 6.25% in the children who received VarV inoculation. The protective effect(VE) of VarV reached 86.25%. The VZV nucleic acid test results of 9 herpes fluid samples were all positive. After the SNP analysis to the ORF22, ORF38 and ORF62, all VZV strains were of Clade2 type of wild strains. Conclusions This varicella outbreak was related to the low immune level of the population. The prevalent strain of VZV was the Clade2 type of wild strain. Health education should be carried out to improve the inoculation rate of VarV.