深圳市一起新型冠状病毒Omicron BF.7变异株暴发疫情的流行病学特征

Epidemiological characteristics of a 2019-nCoV outbreak caused by Omicron variant BF.7 in Shenzhen

目的分析深圳市一起广东省外输入的新型冠状病毒(新冠病毒)Omicron BF.7变异株所致暴发疫情的流行病学特征,梳理和分析其传播链条和传播特征。方法采用现场流行病学方法对病例进行调查,整理新冠病毒感染者活动轨迹、分析代际关系等,对新冠病毒核酸阳性标本进行基因测序分析。结果2022年10月8-23日,深圳市共报告196例新冠病毒感染者,均存在流行病学关联。男、女性分别为100和96例,年龄M(Q_(1),Q_(3))为33(25,46)岁。本起疫情由在广东省外旅游返回深圳市的新冠病毒感染者(首发病例)引起,4条传播链分别为首发病例现住址相关感染8例、7日晚社会面活动相关感染65例、8日写字楼工作场所相关感染累计48例、在工作场所附近的写字楼相关感染74例。本起疫情潜伏期M(Q_(1),Q_(3))为1.44(1.11,2.17)d。室内暴露的潜伏期短于室外暴露的潜伏期,M(Q_(1),Q_(3))分别为1.38(1.06,1.84)和1.95(1.22,2.99)d,差异有统计学意义(Waldχ^(2)=10.27,P=0.001)。随着代际的增加,基因位点突变个数及突变比例增加。在同一传播链疫情时,传播1代的新增基因突变位点1~3个的占比较高。结论本起疫情传播链清晰,新冠病毒Omicron BF.7变异株的潜伏期短,传播速度快,基因突变比例较高。在疫情处置时,应加快疫情处置速度,严格落实防控政策。

Objective To explore the epidemiological characteristic of a COVID-19 outbreak caused by 2019-nCoV Omicron variant BF.7 and other provinces imported in Shenzhen and analyze transmission chains and characteristics.Methods Field epidemiological survey was conducted to identify the transmission chain,analyze the generation relationship among the cases.The 2019-nCoV nucleic acid positive samples were used for gene sequencing.Results From 8 to 23 October,2022,a total of 196 cases of COVID-19 were reported in Shenzhen,all the cases had epidemiological links.In the cases,100 were men and 96 were women,with a median of age,M(Q_(1),Q_(3))was 33(25,46)years.The outbreak was caused by traverlers initial cases infected with 2019-nCoV who returned to Shenzhen after traveling outside of Guangdong Province.There were four transmission chains,including the transmission in place of residence and neighbourhood,affecting 8 persons,transmission in social activity in the evening on 7 October,affecting 65 persons,transmission in work place on 8 October,affecting 48 persons,and transmission in a building near the work place,affecting 74 persons.The median of the incubation period of the infection,M(Q_(1),Q_(3))was 1.44(1.11,2.17)days.The incubation period of indoor exposure less than that of the outdoor exposure,M(Q_(1),Q_(3))was 1.38(1.06,1.84)and 1.95(1.22,2.99)days,respcetively(Waldχ^(2)=10.27,P=0.001).With the increase of case generation,the number and probability of gene mutation increased.In the same transmission chain,the proportion of having 1-3 mutation sites was high in the cases in the first generation.Conclusions The transmission chains were clear in this epidemic.The incubation period of Omicron variant BF.7 infection was shorter,the transmission speed was faster,and the gene mutation rate was higher.It is necessary to conduct prompt response and strict disease control when epidemic occurs.