Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (COVID-19)

Ruiyun Li; Sen Pei; Bin Chen; Yimeng Song; Tao Zhang; Wan Yang; Jeffrey Shaman

Finally, we also modelled the transmission of COVID-19 in China after January 23, when greater control measures were effected. These control measures included travel restrictions imposed between major cities and Wuhan; self-quarantine and contact precautions advocated by the government; and more available rapid testing for infection confirmation [12] [13] . These measures along with changes in medical careseeking behaviour due to increased awareness of the virus and increased personal protective behavior (e.g. wearing of facemasks, social distancing, self-isolation when sick), likely altered the epidemiological characteristics of the outbreak after January 23. To quantify these differences, we re-estimated the system parameters using the metapopulation model-inference framework and city-level daily cases reported between January 24 and February 8. As inter-city mobility was restricted, we set = 0. In addition, to represent reduced person-to-person contact and increased infection detection, we updated the initial priors for and to [0.2, 1.0] and [0.2, 1.0], respectively (see Supplementary Appendix for more details).