Fig. 1 Evolution of CT characteristics of pulmonary lesions in patients with COVID-19. The time intervals after disease onset (days) were divided into 5 groups, i.e., days 0–3 (lesion number = 114), days 4–7 (lesion number = 241), days 8–10 (lesion number = 189), days 11–14 (lesion number = 178), and days 15–21 (lesion number = 95). GGO, ground glass opacities; mixed attenuation = ground glass opacities + consolidation