北京市某市场新型冠状病毒肺炎相关聚集性疫情传播链分析

目的调查北京市海淀区某商品交易市场(Y市场)相关新型冠状病毒肺炎(COVID-19)聚集性疫情,分析其传播链及传播模式,为COVID-19疫情防控提供参考依据。方法采用现场流行病学和聚集性疫情调查方法,描述COVID-19病例三间分布等流行病学特征,绘制病例发病时序图和分析传播链。采集调查对象呼吸道标本,采用实时荧光RT-PCR法进行新型冠状病毒核酸检测。结果本次COVID-19聚集性疫情的感染来源于北京市丰台区某农产品批发市场(X市场),由Y市场1名从业人员暴露于X市场引发,随后在Y市场、周边社区、美食城、公司、家庭等地导致8起聚集性疫情,共报告关联性COVID-19确诊病例20例,无症状感染者1例。发病时间主要集中在6月10-14日,男性8例,女性13例;年龄中位数为45岁,年龄范围5~87岁;首发症状以发热(10/20)、咽部不适(7/20)为主;潜伏期中位数5(IQR:3~8)d;代间距中位数5 d;续发率3.7%(20/538),家庭密切接触者续发率14.0%(7/50)。结论Y市场COVID-19疫情是通过被污染环境、物品、人员接触等多种暴露方式导致的聚集性疫情,北京市海淀区通过综合防控措施使COVID-19疫情得到有效控制。

Transmission chains of clusters of COVID-19 associated with a market in Beijing

Objective To investigate the clusters of COVID-19 associated with a market (market Y) in Haidian District, Beijing, and analyze the chain of transmission and provide reference for effective prevention and control of COVID-19. Methods The investigation of field epidemiology and cluster epidemic was used to describe the distributions of all COVID-19 cases. The time sequence diagram of the cases, disease onset was drawn and transmission chains were analyzed. Real-time RT-PCR assay was conducted for SARS-CoV-2 nucleic acid test by using the respiratory samples of the cases. Results The COVID-19 epidemic, originated from a wholesale farm produce market (market X) in Fengtai District, Beijing, was introduced by a marketer in the market Y who had exposed to market X, causing 8 clusters of 20 confirmed cases of COVID-19 and one asymptomatic case, including 8 men and 13 women, in market Y, surrounding communities, food plaza, companies,families and other places. The incidence peaked during June 10-14, 2020; the median age of the cases was 45 years, ranging from 5 years to 87 years. The initial symptoms of the cases included fever (10/20) and pharynx discomfort (7/20). The median of incubation period was 5 days (IQR:3-8). The median of serial interval between primary case and secondary cases was 5 days with a secondary attack rate of 3.7%(20/538), and the secondary attack rate in household close-contacts was 14.0% (7/50). Conclusions The clusters of COVID-19 associated with market Y were caused by several modes of transmission, including human-to-human, contaminated material-to-human, etc. The combined public-health response measures were effective to control the COVID-19 epidemic in Haidian district of Beijing.