广州市Delta变异毒株导致COVID-19疫情的流行病学参数估计

Estimation of epidemiological parameters of COVID-19 epidemic caused by Delta variant strain in Guangzhou

目的调查广州市一起输入型Delta变异毒株引起的COVID-19疫情,分析其传播链及传播特征,为预测疾病发展及疫情防控提供理论依据。方法通过收集广州市官方发布的信息,从中选择具有明确传播链的确诊病例,计算此次疫情传播的代间隔(serial interval, SI)、基本再生数(R;)以及实时再生数(R;)等传染病指标,分析其流行病学特征。结果 2021年5月21日-6月20日,广州市累计确诊144例本土COVID-19病例,从中选择具有明确传播链的67对病例,计算SI服从Gamma分布,均数为4.27 d,标准差为2.65 d。R_(1)=3.18(95%CI:2.197~4.428),R;随着时间推移呈现出下降趋势,于6月10日,R_(1)=0.97(95%CI:0.751~1.214),下降到1.00以下。此后R_(1)一直<1.00,并且随着时间变化,越来越小。结论此次COVID-19疫情的SI较短而R;较大,表明Delta变异毒株相比于2020年武汉感染的SARS-CoV-2具有更快的传播速度以及更强的传播力。

Objective An epidemic of COVID-19 caused by an imported Delta variant strain in Guangzhou was investigated, and the transmission chain, transmission characteristics and infection of each case were analyzed, so as to provide a theoretical basis for predicting disease development and epidemic prevention and control. Methods By collecting the information released by Guangzhou government, the confirmed cases with a clear transmission chain were selected, and the infectious disease indicators such as serial interval(SI), basic reproduction number(R_(1)) and time-dependent reproduction number(R;) were calculated to analyze the epidemiological characteristics. Results From May 21 to June 20, 2021, a total of 144 cases of indigenous COVID-19 were confirmed in Guangzhou, among which 67 pairs of cases with a clear transmission chain were selected. SI was calculated to follow the Gamma distribution, with a mean of 4.27 d and a standard deviation of 2.65 d. R_(1)=3.18(95% CI: 2.197-4.428), and R;showed an obvious decreasing trend over time. On June 10, R_(1)=0.97(95% CI: 0.751-1.214), which was lower than 1. Since then Rt had been less than 1, and it got smaller and smaller over time. Conclusion In this COVID-19 epidemic, the SI was shorter and the R;was larger, which indicated that the Delta variant strain had a faster transmission rate and stronger transmissibility than the COVID-19 infected in Wuhan in 2020.