中山市新冠病毒变异株JN.1及其子分支感染者及家庭续发特征分析

Epidemic characteristics of the COVID-19 variant JN.1 and its subbranch case and household transmission in Zhongshan city

目的了解新冠病毒变异株JN.1在中山地区的流行特征。方法采集中山市各级医疗机构报告的新冠病毒感染个案的咽拭子开展核酸检测和基因测序,对测序结果为JN.1及其子分支的感染个案进行描述性流行病学特征分析,并采集同住家人的咽拭子样本进行检测,计算家庭续发率。结果2023年12月22日-2024年2月21日,共监测发现23株新冠病毒变异株JN.1及其子分支,占有效序列测序样本的79.31%(23/29)。其中,20株为JN.1占68.97%(20/29),2株为JN.1.4,1株为JN.1.5。23例变异株JN.1及其子分支感染个案的临床表现均为轻症;首次感染者占39.13%(9/23);境外输入及相关个案占30.43%(7/23);发生续发的家庭占比为25.00%(4/16),家庭成员续发率为13.51%(5/37,95%CI:1.96%~25.07%)。有3个续发家庭的代间距为5 d,1个续发家庭的代间距为13 d。家庭续发率在年龄、性别、是否既往感染或接种疫苗、家庭成员数等因素间的差异均无统计学意义(P>0.05)。结论变异株JN.1及其子分支为优势流行株,人群普遍易感,但在现时人群免疫力水平下其传播力有限,感染后临床症状表现较轻。考虑到病毒变异、人群免疫力等因素,需持续做好监测,保持关注。

Objective To investigate the epidemic characteristics of coronavirus disease 2019(COVID-19)variant JN.1 in Zhongshan city.Methods The throat swabs of all the COVID-19 infection cases reported by medical institutions in Zhongshan city were collected for nucleic acid detection and gene sequencing.Descriptive epidemiological analysis and household transmission analysis were carried out based on the sequencing results of JN.1 and its subbranches.Results From December 22,2023 to February 21,2024,23 cases of variant JN.1 and its subbranches were found,accounting for 79.31%(23/29)of the effective sequencing samples.Among them,20 cases were JN.1(68.97%,20/29),2 cases were JN.1.4,and 1 case was JN.1.5.All cases of variant JN.1 and its subbranches had mild symptoms;39.13%(9/23)were the first-time infected individuals;imported and related cases accounted for 30.43%(7/23);25.00%(4/16)of the families developed secondary cases,and the household transmission rate was 13.51%(5/37,95%CI:1.96%-25.07%).The generation interval was 5 days in three families,and 13 days in one family.There was no statistically significant difference in household transmission rate among factors such as age,gender,experienced of infection or vaccination,and family members.Conclusions The variant JN.1 and its subbranches were currently the dominant epidemic strains,and the people was generally susceptible.However,because of the current level of population immunity,the transmission ability was limited,and the clinical symptoms were relatively mild.Considering the virus mutations and population immunity,continuous monitoring should be necessary to reduce the transmission of the virus.