Pan X X, Chen Y, Wang A H, Wang J M, Ye L X, Gu S H, Fang T, Xu G Z
Ningbo Prefectural Center for Disease Control and Prevention, Ningbo 315010, China.
Zhonghua Liu Xing Bing Xue Za Zhi. 2020 Dec 10;41(12):2010-2014. doi: 10.3760/cma.j.cn112338-20200330-00466.
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 ((0)) of COVID-19. 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 (0) was calculated based on the SEIR model. 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 (=0.551). According to the Tg calculated in this paper, the (0) of COVID-19 in Ningbo was 3.06 (95: 2.64- 3.51); according to the reported case transmission interval of 7.5 days in the literature, the (0) was 3.32 (95: 2.51-9.38). 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.
描述浙江省宁波市新型冠状病毒肺炎（COVID-19）病例聚集性的基本特征，并评估COVID-19的代间距（Tg）和基本再生数（R0）。调查宁波市COVID-19病例聚集性的基本信息和发病时间，采用伽马分布拟合病例的代间距，并基于SEIR模型计算R0。在15起COVID-19病例聚集性事件中，共有52例确诊病例，5例核酸阳性无症状感染者。病例发生时间为1月23日至2月4日，病例以女性为主。潜伏期为（6.11±3.38）天，中位数为5天。Tg为（6.93±3.70）天。年龄＜60岁组与≥60岁组、男性与女性之间的Tg差异无统计学意义（P=0.551）。根据本文计算的Tg，宁波市COVID-19的R0为3.06（95%CI：2.64-3.51）；根据文献报道病例传播间隔为7.5天计算，R0为3.32（95%CI：2.51-9.38）。宁波市COVID-19病例聚集性的Tg无年龄和性别差异，且COVID-19在早期具有较高的传染性和传播力。
