Fig. 4

The top panel corresponds to the epidemic in Xi’an, and the bottom panel corresponds to the epidemic in Shanghai. Bars in light gray and in dark gray represent the number of daily reported cases in control zones and in society, respectively. The black curve is the median effective reproduction number \({R}_{t}^{{s}_{2}}\) through time \(t\) in society, which is calculated by assuming that there are internal infections in the control zone. The gray is the 95% confidence interval for the predicted \({R}_{t}^{{s}_{2}}\). The size of \({R}_{t}^{{s}_{2}}\) is measured by the right y-axis. When \({R}_{t}^{{s}_{2}}\) is above the threshold value of one, i.e., the horizontal dashed line in red, the epidemic shows an upward trend; otherwise, it is under control