Fig. 4

Geographical distribution of change (quantified by percentage) of cumulative COVID-19 cases in comparison with baseline (the presence of both chunyun and lock-down) by February 9, 2020, depicted from Dr. Hu’s own work. a, scenario 1 (lock-down without chunyun); b, scenario 2 (chunyun without lock-down); c, scenario 3 (the absence of both chunyun and lock-down); d, location of urban agglomeration. This figure was produced in ArcGIS 10.4.1 (ESRI, Redlands, CA, USA) using shape files representing China’s municipal-level administrative units freely downloaded from Resource and Environment Science and Data Center (http://www.resdc.cn/data.aspx?DATAID=201)