Objective To describe the variation in the transmission of coronavirus disease 2019 (COVID-19) and its association with dynamic public health interventions in mainland China.
Methods The daily numbers of new confirmed cases, severe cases and asymptomatic infected cases of COVID-19 reported from January 10 to July 10, 2020 were analyzed. In accordance with the transmission trajectory and overall guidelines for prevention and control of COVID-19 epidemic in mainland China, we divided this epidemic period into three phases. We calculated the effective reproductive number (Rt) of COVID-19 in different phases to evaluate variations in COVID-19 transmission and the effect of intervention measures.
Results A total of 83 587 confirmed cases, 1 964 imported confirmed cases and 2 402 asymptomatic infections of COVID-19 were reported in mainland China during the period and the daily number of severe cases gradually decreased. The majority of confirmed cases and severe cases of COVID-19 occurred mainly in the first phase and the Rt reached the highest of 10.75 (95% confidence interval: 10.26 – 11.24); then the Rt value decreased to less than 1.0 on February 19 and the epidemic was under effective control. In the second phase, the Rt value fluctuated within a small range due to the increase of imported cases. In the third phase, the number of confirmed cases increased slightly in 44 regions of moderate or high transmission risk in Beijing city, resulting in a minor increment of Rt value, but the epidemic rebound was controlled after 12 days.
Conclusion In the prevention and control of the COVID-19 epidemic, China has adopted targeted dynamic public health measures based on the epidemic characteristics in different stages to control the epidemic effectively. The epidemic response could provide a positive reference for China and other countries in prevention and control of similar infectious disease epidemics.
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