Dynamics of the coronavirus disease 2019 (COVID-19) epidemic in Wuhan City, Hubei Province and China: a second derivative analysis of the cumulative daily diagnosed cases during the first 85 days

BACKGROUND: Controlling the coronavirus disease 2019 (COVID-19) epidemic requires information beyond new and cumulative cases. This study aims to conduct an in-depth analysis by geographic strata: Wuhan City (hereafter referred to as Wuhan) only, Hubei Province (hereafter referred to as Hubei) excluding Wuhan, and China excluding Hubei. METHODS: Daily cumulative confirmed COVID-19 cases between December 8, 2019 (the date of symptom onset based on patients’ recall during the investigation), and March 1, 2020, from official sources and published studies were analyzed. The second derivative model was used for information extraction. Data analysis was conducted separately for the three strata. RESULTS: A total of 80 026 diagnosed COVID-19 cases were reported during the first 85 days of the epidemic, with 49 315 cases from Wuhan, 17 788 from Hubei excluding Wuhan, and 12 923 from China excluding Hubei. Analytical results indicate that the COVID-19 epidemic consists of an Acceleration, a Deceleration, and a Stabilization Phase in all three geographic strata, plus a Silent Attack Phase for Wuhan only. Given the reported incubation period of 14 days, effects of the massive anti-epidemic actions were revealed by both the Acceleration and Deceleration Phases. The Acceleration Phase signaled the effect of the intervention to detect the infected; the Deceleration Phase signaled the declines in new infections after the infected were detected, treated and quarantined. CONCLUSION: Findings of the study provide new evidence to better monitor the epidemic, evaluate its response to intervention, and predict the trend long. In addition to re-evaluating the control of the COVID-19 epidemic in China, this study provided a model for monitoring outbreaks of COVID-19 in different countries across the world.