宁波市15起新型冠状病毒肺炎聚集性疫情的传播力研究

目的 描述新型冠状病毒肺炎（COVID-19）聚集性疫情病例的基本特征。方法 收集15起COVID-19聚集性疫情病例的基本信息，采用伽马分布拟合病例代际间隔时间（Tg），使用基于SEIR模型计算基本再生数（R₀）。结果 15起聚集性疫情中共有确诊病例52例、涉及5例核酸阳性无症状感染者。病例发病时间主要集中在1月23日至2月4日，以女性为主，潜伏期为（6.11±3.38）d。Tg为（6.93±3.70）d，在<60岁、≥60岁组及男、女性之间，Tg差异无统计学意义（P=0.551）。按照本研究估算的Tg计算，宁波市新冠肺炎感染的R₀为3.06（95% CI：2.64~3.51）；按照文献报告的病例Tg为7.5 d计算，R₀为3.32（95% CI：2.51~9.38）。结论 COVID-19聚集性疫情病例的Tg在不同年龄、性别间差异不大，COVID-19早期致病和传播力较高。

Study on transmission dynamic of 15 clusters of COVID-2019 cases in Ningbo

Objective To describe the basic characteristics of clusters of coronavirus diseases 2019 (COVID-19) cases in Ningbo, Zhejiang province, and evaluate the generation time (Tg) and basic reproduction number (R₀) of COVID-19. Methods The basic information and onset times of the clusters of COVID-19 cases in Ningbo were investigated, the inter-generational interval of the cases were fitted by using gamma distribution, and the R₀ was calculated based on the SEIR model. Results In the 15 clusters of COVID-19 cases, a total of 52 confirmed cases, 5 cases of nucleic acid-positive asymptomatic cases. The cases occurred from January 23 to February 4, the cases were mainly women. The incubation period was (6.11±3.38) days, and the median was 5 days. The Tg was (6.93±3.70) days. There were no significant differences in Tg between age group <60 years and age group 60 years and above, and between men and women (P=0.551). According to the Tg calculated in this paper, the R₀ of COVID-19 in Ningbo was 3.06 (95% CI:2.64-3.51); according to the reported case transmission interval of 7.5 days in the literature, the R₀ was 3.32 (95% CI:2.51-9.38). Conclusion There is no age and gender specific differences in the Tg of clusters of COVID-19 cases in Ningbo, and COVID-19 has high infectivity and spreading power in early phase.