Table 3 Frequency of chest CT findings in COVID-19 CT signs Frequency Stage Ground glass opacity ++++ E/A/S Consolidation without ground glass opacity ++ S Ground glass opacity and crazy paving ++ E/A/S Ground glass opacity with consolidation +++ E/A/S Patchy ground glass opacity +++ E Bilateral distribution ++++ E/A/S/D Peripheral distribution +++ E Air bronchogram ++ E/A/S Pleural effusion + S Strip-like opacity + D The appearance frequency of each CT characteristic is described in order from low to high as (+~++++); E, A, S, and D stand for stage early, advanced, severe, and dissipation