宁波市15起新型冠状病毒肺炎聚集性疫情的传播力研究

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

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。

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.