[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.