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

where Q o t is the official number of actively infected and quarantined cases by day t. It is worth noting that daily number of newly infected cases dramatically increased to 13,436 on February 12, 2020 from 1,104 the day before, according to CCDC. This surge was attributed to the change of government criteria for confirming infections. Before February 12, 2020, only those tested positive by test kits were considered as infected. Starting from February 12, 2020, an infection was confirmed either based on positive testing result or through clinical diagnosis using computed tomography (CT) scans. As a result, suspected infections by CT scans before February 12, 2020 were relabeled as confirmed infections on February 12, 2020. It is therefore necessary to adjust the number of newly infected cases on February 12, 2020 (i.e., 13,436) by reallocating this number to days prior to and including February 12, 2020, proportional to the number of daily suspected cases in these days.