Early epidemiological assessment of the transmission potential and virulence of 2019 Novel Coronavirus in Wuhan City: China, 2019-2020

Mizumoto, Kenji; Kagaya, Katsushi; Chowell, Gerardo

BackgroundSince the first cluster of cases was identified in Wuhan City, China, in December, 2019, coronavirus disease 2019 (COVID-19) has rapidly spread across China, causing multiple introductions in 109 countries/territories/areas as of March 10th. Despite the scarcity of publicly available data, scientists around the world have made strides in estimating the magnitude of the epidemic, the basic reproduction number, and transmission patterns. Recently more evidence suggests that a substantial fraction of the infected individuals with the novel coronavirus show little if any symptoms, which suggest the need to reassess the transmission potential of this emerging disease. In this study, we derive estimates of the transmissibility and virulence of COVID-19 in Wuhan City, China, by reconstructing the underlying transmission dynamics using multiple data sources. MethodsWe employ statistical methods and publicly available epidemiological datasets to jointly derive estimates of transmissibility and severity associated with the novel coronavirus. For this purpose, the daily series of laboratory-confirmed COVID-19 cases and deaths in Wuhan City and epidemiological data of Japanese evacuees from Wuhan City on board government-chartered flights were integrated into our analysis. ResultsOur posterior estimates of basic reproduction number (R) in Wuhan City, China in 2019-2020 reached values as high as 5.20 (95%CrI: 5.04-5.47) and the enhanced public health intervention after January 23rd in 2020 was associated with a declined R at 0.58 (95%CrI: 0.51-0.64), with the total number of infections (i.e. cumulative infections) estimated at 1905526 (95%CrI: 1350283- 2655936) in Wuhan City, raising the proportion of infected individuals to 19.1% (95%CrI: 13.5-26.6%). We also found that most recent crude infection fatality ratio (IFR) and time-delay adjusted IFR is estimated to be 0.04% (95% CrI: 0.03%-0.06%) and 0.12% (95%CrI: 0.08-0.17%), which is several orders of magnitude smaller than the crude CFR estimated at 4.19% ConclusionsWe have estimated key epidemiological parameters of the transmissibility and virulence of COVID-19 in Wuhan, China during January-February, 2020 using an ecological modelling approach. The power of our approach lies in the ability to infer epidemiological parameters with quantified uncertainty from partial observations collected by surveillance systems.