北京市3起新型冠状病毒Omicron变异株聚集性疫情的感染来源和传播链分析题录

目的对北京市3起可能通过跨境物流途径导致的新型冠状病毒(新冠病毒)Omicron变异株聚集性疫情进行调查, 分析其感染来源和传播链。方法应用流行病学调查和大数据技术核查病例的活动轨迹, 对活动轨迹涉及的风险点位进行密切接触者追踪、人员和环境采样, 应用实时荧光定量PCR进行核酸检测, 对核酸阳性标本进行基因测序分析。结果 2022年1-4月北京市3起Omicron变异株聚集性疫情病毒基因序列分别为Omicron变异株BA.1、BA.1.1、BA.2分支, 疫情分别持续8、12、8 d, 报告6、42、32例新冠病毒感染者。1起感染来源可能为国际邮件, 2起可能为进口衣物, 进口物品从境外启运至首发病例接触感染的时间间隔为3～4 d。潜伏期M(Q1, Q3)为3(2, 4)d, 代间距M(Q1, Q3)为3(2, 4)d。结论此次疫情提示常温进口货品通过物流途径输入Omicron变异株疫情的风险, 且Omicron变异株传播速度更快, 应加快流行病学调查处置。

Analysis on infection sources and transmission chains of three outbreaks caused by 2019-nCoV Omicron variant in Beijing, China

Objective To investigate the infection sources and the transmission chains of three outbreaks caused by 2019-nCoV Omicron variant possibly spread through cross-border logistics in Beijing. Methods Epidemiological investigation and big data were used to identify the exposure points of the cases. Close contacts were traced from the exposure points, and the cases'' and environmental samples were collected for nucleic acid tests. Positive samples were analyzed by gene sequencing. Results The Omicron variant causing 3 outbreaks in Beijing from January to April, 2022 belonged to BA.1, BA.1.1 and BA.2. The outbreaks lasted for 8, 12 and 8 days respectively, and 6, 42 and 32 cases infected with 2019-nCoV were reported respectively. International mail might be the infection source for 1 outbreak, and imported clothes might be the infection sources for another 2 outbreaks. The interval between the shipment start time of the imported goods and the infection time of the index case was 3-4 days. The mean incubation period (Q₁, Q₃) was 3 (2, 4) days and the mean serial interval (Q₁, Q₃) was 3 (2, 4)days. Conclusions The 3 outbreaks highlighted the risk of infection by Omicron variant from international logistics-related imported goods at normal temperature. Omicron variant has stronger transmissibility, indicating that rapid epidemiological investigation and strict management are needed.