北京市一起新型冠状病毒Omicron变异株聚集性疫情特征分析

Epidemiological characteristics of an epidemic of 2019-nCoV Omicron variant infection in Beijing

目的分析北京市海淀区一起新型冠状病毒肺炎聚集性疫情流行病学特征及传播链。方法采用描述性流行病学方法分析疫情流行病学特征,应用现场调查和大数据技术分析传播链。结果2022年4月27日至5月13日,海淀区发生一起新型冠状病毒肺炎聚集性疫情,全基因组测序系Omicron变异株(BA.2.2进化分支);涉及感染者38例,确诊病例34例,无症状感染者4例;临床分型以轻型(88.2%)为主,无重型、危重型和死亡病例;早期临床症状以咽部不适(50.0%)、咳嗽(29.4%)为主;17 d内传播7代,涉及3起社区聚集、2起单位聚集和8个家庭内传播;暴露方式以同住(47.6%)、同时空暴露(31.6%)为主;代间距M(Q_(1),Q_(3))为3(1,6)d;总续发率为1.5%(37/2482),其中家庭续发率为36.7%(18/49)。结论本起Omicron变异株疫情临床症状轻,家庭、社区聚集性明显,疫情传播速度较快,同时空暴露感染风险较高,需利用信息化技术全面摸排密切接触者,以快制快,有效阻断疫情传播。

Objective To analyze the epidemiological characteristics and transmission chain of an epidemic of COVID-19 in Haidian district,Beijing.Methods Descriptive epidemiological method was used to analyze the epidemiological characteristics of the epidemic,and field investigation and big data technology were used to analyze the transmission chain of the epidemic.Results From April 27 to May 13,2022,an epidemic of COVID-19 occurred in Haidian district.The strains isolated from the cases were identified by whole genome sequencing as Omicron variant(BA.2.2 evolutionary branch).A total of 38 infection cases were detected,including 34 confirmed cases and 4 asymptomatic cases.Most cases were mild ones(88.2%),no severe,critical or death cases occurred.The early clinical symptoms were mainly sore throat(50.0%)and cough(29.4%).The epidemic lasted for 17 days,resulting in 7 generations of the cases and involving 3 community transmissions,2 working place transmissions and 8 family transmissions;the main infection routes were co-residence(47.6%)and co-space exposure(31.6%).The intergenerational interval M(Q_(1),Q_(3))was 3(1,6)days.The overall secondary attack rate was 1.5%(37/2482),and the family secondary attack rate was 36.7%(18/49).Conclusions The cases in this COVID-19 epidemic caused by Omicron variant had mild clinical symptoms,but the case clustering in families and communities was obvious,the transmission was rapid,and the risk for co-space exposure was high.It is necessary to use information technology to identify close contacts in the local population for the rapid and effective blocking of the epidemic spread.