Estimation of real-time basic reproduction number and epidemic status of 2019 novel coronavirus diseases(COVID-19) in first-tier cities

Objective To analyze the epidemic status of COVID-19,and its prevention and control in Beijing,Shanghai,Guangzhou and Shenzhen,and provide scientific evidence for COVID-19 prevention and control. Methods Based on publicly available data from the website of National Health Commission of the People's Republic of China,a mature model was used to estimate the dynamic change of R₀ at different time points （R₀ t）,so as to evaluate the trend of COVID-19 infectivity over time under the existing prevent measures. Results As of 24:00 on February 25,400,336,346,and 417 patients with COVID-19 were diagnosed in Beijing,Shanghai,Guangzhou,and Shenzhen,respectively.The four cities had the highest single-day diagnosis from January 30 to February 2.The number of new cases per day began to decline from February.On February 3 and within 3-5 days after February 10,the daily increase in the number of new cases in each of the four cities showed a brief upward trend.R₀（t） in Beijing,Shanghai and Guangzhou was at the highest value within one week at the beginning of the outbreak,which was 8.37 （95% CI:6.62-10.41）,7.11 （95% CI:5.46-9.06）,9.29 （95% CI:7.1-11.88）,respectively,and then continued to decline.R₀（t） in Shenzhen reached its highest value on January 31,at 5.85 （95% CI:4.98-6.81）,and then declined gradually.The R₀（t） of the four cities all dropped to 1 on the 21st day （February 10） of the outbreak,and remained below 1. Conclusion As of February 25,the epidemic situation in four first-tier cities is currently under effective control.The movement of returning to work and study may have an impact on the epidemic situation.Besides,first-tier cities should pay attention to the risk of overseas epidemic import.