The time-varying transmission dynamics of COVID-19 and synchronous actions in China.

Abstract Objectives We aimed to estimate the time-varying transmission dynamics of COVID-19 in China, Wuhan City and Guangdong province, and compared them with that of severe acute respiratory syndrome (SARS). Methods Data on COVID-19 cases by March 20, 2020 in China was collected from epidemiological investigations or official websites. Data on SARS cases in Guangdong Province, Beijing and Hong Kong during 2002-2003 were also obtained. We estimated the doubling time, basic reproduction number (R0) and time-varying reproduction number (Rt) of COVID-19 and SARS. Results As of March 20, 2020, 80,739 COVID-19 indigenous cases were identified in mainland China. Most cases were reported between January 20 and February 29. The R0 of COVID-19 nationwide and in Wuhan were 5.0 and 4.8 respectively, which were greater than R0 of SARS in Guangdong (R0=2.3), Hong Kong (R0 = 2.3), and Beijing (R0 = 2.6). During the epidemic of COVID-19, the Rt nationwide first increased to a peak of 8.4 and declined quickly to below 1 in one month. In terms of SARS, the Rt curve saw a fluctuation change with more than one peak though the peak was lower than COVID-19. Conclusions COVID-19 has much higher transmissibility than SARS, and a series of major actions for suppressing the outbreak are effective. However, persistent efforts are needed to prevent the rebound of the epidemic in the context of the global pandemic.