^ Period 1: before the announcement of human to human transmission (Dec 31, 2019 to Jan 18, 2020); Period 2: From the announcement of human to human transmission to traffic restrictions (Jan 19, 2020 to Jan 23, 2020); Period 3: Traffic restrictions (Jan 24, 2020 to Mar 27, 2020); Period 4: Traffic restrictions dismissed (Mar 28, 2020 to Apr 11, 2020).
***p<0.001,**p<0.01,*p<0.05