Table 1.

Lung histopathology scoring system.

Score	Observations
0	Normal, no significant finding
1	Minor inflammation with slight thickening of alveolar septa and sparse monocyte infiltration
2	Apparent inflammation, alveolus septa thickening with more interstitial mononuclear inflammatory infiltration
3	DAD, with alveolus septa thickening, and increased infiltration of inflammatory cells
4	DAD, with extensive exudation and septa thickening, shrinking of alveoli, restricted fusion of the thick septa, obvious septa hemorrhage and more cell infiltration in alveolar cavities
5	DAD, with massive cell filtration in alveolar cavities and alveoli shrinking, sheets of septa fusion, and hyaline membranes lining the alveolar walls

DAD diffuse alveolar damage.