2021年宁波市一起新型冠状病毒Delta变异株本土聚集性疫情流行特征分析

Epidemiological characteristics of a local cluster epidemic caused by 2019-nCoV Delta variant in Ningbo,2021

目的分析宁波市一起新型冠状(新冠)病毒Delta变异株本土聚集性疫情流行特征,为完善新型冠状病毒肺炎(COVID-19)疫情防控政策提供参考依据。方法通过制定病例定义,开展病例搜索,对发现的病例开展现场流行病学调查,采集相关标本开展病原学检测,运用描述流行病学方法进行分析。结果本起疫情累计报告74例确诊病例,病例以轻型为主,占87.84%(65/74),无重型和危重型。流行曲线呈人传人传播模式,据流行病学调查显示,本起疫情至少传播6代。病例年龄范围为2~80岁,其中≥60岁占27.03%(20/74)。职业分布中以工人占55.41%(41/74)和家务/待业占27.03%(20/74)为主,疫情局限,未发生病例外溢。病例间流行病学关联明确,传播链清晰。基因测序结果证实为新冠病毒Delta变异株,与浙江省外输入关联疫情高度同源。结论本起疫情为一起浙江省外输入COVID-19确诊病例引起的本土聚集性疫情,通过生活、工作接触导致社区传播扩散。

Objective To understand the epidemiological characteristics of a local clustered epidemic caused by 2019-nCoV Delta variant in Ningbo and provide reference for the improvement of COVID-19 epidemic prevention and control.Methods Case finding was conducted based on case definitions,and field epidemiological investigation of COVID-19 cases was carried out.In which Nasal and oropharyngeal swabs of the cases were collected for pathogen testing,and the results were analyzed with descriptive epidemiological methods.Results A total of 74 COVID-19 cases were reported in this epidemic,and the cases were mainly mild ones,accounting for 87.84%(65/74),and there were no severe or critical cases.The epidemic curve showed a human-to-human transmission mode,indicating that a transmission for at least six generations had occurred.The age of the COVID-19 patients ranged from 2 years to 80 years,and 27.03%(20/74)of the cases were older than 60 years.The cases were mainly workers(55.41%,41/74)and housework/the unemployed(27.03%,20/74).The COVID-19 epidemic was limited,and no further spread to other areas occurred.The transmission chain among the cases was clear,and the gene sequencing results confirmed that the current epidemic was caused by 2019-nCoV Delta variant,which was highly homologous to the strains from other province.Conclusion The local COVID-19 epidemic in Ningbo was caused by imported cases of COVID-19 from other province,and local community spread occurred through daily contacts between cases and contacts.