Dynamic Estimation of Epidemiological Parameters of COVID-19 Outbreak and Effects of Interventions on Its Spread

Hongzhe Zhang; Xiaohang Zhao; Kexin Yin; Yiren Yan; Wei Qian; Bintong Chen; Xiao Fang

In summary, our finding provides a quantitative illustration that the scale of infection size in Wuhan can be multi-fold higher than officially reported numbers and partially explains the excessive stress experienced by frontline medical workers despite seemingly modest case number increases reported during late January of 2020. This work thus gives a cautionary tale for drawing immediate public health conclusions solely based on unadjusted official case numbers that do not necessarily give a complete overall picture for pandemic situation in outbreak early periods. In addition, by examining the temporal trajectory of effective reproduction numbers, we can clearly see the gradual control effects of COVID-19 in Wuhan soon after the implementation of city-wide lockdown and suspension of all non-essential vehicle operation to reduce the contact rate among Wuhan residents; the aggressive increase of testing and hospital capacity further brought down the effective reproduction number rapidly by shortening infectious period of positive carriers and reducing new cross-infection cases from close family and community contacts. Our study affirms the believed importance and effectiveness of imposing tight non-essential travel restrictions (which may also include, e.g., the shelter-in-place and stay-at-home orders) early on, as well as swiftly addressing the testing shortage issues and avoiding hospital overcrowding for effective mitigation of COVID-19 community spread.