Radiological and clinical spectrum of COVID-19: A major concern for public health

Table 1 Disease progression and its associated radiological changes[56-58]

Stages	Periods	Clinical findings
Early-stage	< 2 d	(1) More than half of the patients have a negative chest result; (2) It shows single or multiple GGO, nodule small patchy GGO, or large patchy GGO; (3) The lesions are located predominately in the middle and lower lung lobes with subpleural, peri-fissure, or peri-bronchovascular distribution; (4) The thickening of the bronchial wall, thickening of small vessels, air bronchogram sign and the thickening of adjacent interlobular pleura are common; (5) Some large patchy GGO with subsegmental distribution and increased small vessels seems like the fine grid shadow or "crazy paving” sign; And (6) Some GGO shows "reversed halo" sign
Intermediate stage	3-5 d	(1) Multiple new lesions similar to those in the early stage appeared; (2) Most of the original lesions would enlarge, with the presence of consolidation varying sizes and density; (3) Nodular, halo sign and air bronchogram sign in the consolidation could be seen; (4) Fusion or partial absorption of the original GGOs or consolidation could be seen; And (5) The scope and shape of lesions often changed after the fusion, which might not distribute along with the bronchovascular bundle thoroughly
Late or severe stage	6-12 d	(1) Progression of the disease, diffuse consolidation with increased density would occur; (2) The bronchiectasis and air bronchogram sign appeared; (3) Patchy GGOs were shown in non-consolidated regions; (4) "White lung" appeared when most of the lungs were involved in the severe stage; And (5) Thickened interlobular and bilateral pleura were commonly seen with a small amount of pleural effusion
Resolved stage	> 14 d	(1) After the treatment, most COVID-19 patients tend to be stable and improved, showing that the range of lesions diminished, the density gradually decreased, the number of lesions reduced; (2) The GGO can be fully absorbed; And (3) In some cases, the lesions can evolve into a fibrous cord in a relatively short period

GGO: Ground-glass opacities; COVID-19: Coronavirus disease 2019.