基于传染病动力学模型的宁波市新型冠状病毒肺炎防控措施效果评估

目的 基于传染病动力学模型评估宁波市新型冠状病毒肺炎（COVID-19）防控措施的效果。方法 收集截至2020年3月9日宁波市COVID-19疫情个案数据、疾病进程等信息。根据防控策略落实情况，建立SEIR传染病动力学模型，计算基本再生数（R₀）和实时再生数（R_t），评估防控效果。结果 宁波市累计确诊COVID-19病例157例，无死亡病例，重症病例比例为12.1%。从暴露到发病（潜伏期）平均（5.7±2.9）d，发病到确诊平均（5.4±3.7）d，从确诊到出院平均（16.6±6.5）d。累计医学观察105 339人，其中居家医学观察者COVID-19感染率为0.1%，集中医学观察者感染率为0.3%，确诊病例在就诊前处于医学观察期者占63.1%。估算R₀为4.8。随着防控措施的加强，R_t呈逐渐下降趋势，到2月4日下降至1.0以下，之后持续下降到2月中旬的0.2。结论 通过建立传染病动力学模型，能够有效评估宁波市COVID-19防控措施的效果，为防控策略的制定提供科学依据。

Epidemic dynamic model based evaluation of effectiveness of prevention and control strategies for COVID-19 in Ningbo

Objective To evaluate effectiveness of prevention and control strategies for COVID-19 in Ningbo by using an epidemic dynamic model. Methods The incidence data and epidemic information of COVID-19 reported in Ningbo as of 9 March, 2020 were collected, and based on the implementation of prevention and control strategies, we developed a SEIR epidemic dynamics model. The basic and real-time reproduction numbers were calculated to evaluate effectiveness of prevention and control. Results A total of 157 cases of COVID-19 were confirmed, without death, in Ningbo. The proportion of severe cases was 12.1%. The mean incubation period was estimated to be (5.7±2.9) days. The mean interval from illness onset to diagnosis was (5.4±3.7) days. The mean duration from diagnosis to hospital discharge was (16.6±6.5) days. A total of 105 339 contacts had been under medical observation. The infection rates in contacts with home quarantine and centralized quarantine were 0.1% and 0.3%, respectively. In the confirmed cases, those who had been under medical observation before diagnoses accounted for 63.1%. The basic reproduction number was estimated to be 4.8. With the strengthening of prevention and control measures, real-time reproduction number showed a gradual downward trend, dropping to below 1.0 on 4 February, and then continued to drop to 0.2 in mid-February. Conclusion The effectiveness of the prevention and control measures for COVID-19 in Ningbo can be evaluated by using epidemic dynamic model to provide scientific evidence for the development of the prevention and control strategies.