Table 1.

Scoring system used to define the pathological changes in the lungs.

Score	Area affected	Epithelial degeneration/necrosis	Inflammation
0	None	None	None
1	5−10%	Minimal; scattered cell necrosis/vacuolation affecting 5 to 10% of tissue section	Minimal; scattered inflammatory cells affecting 5−10% of tissue section
2	10−25%	Mild; scattered cell necrosis/vacuolation	Multifocal, few inflammatory cells
3	25−50%	Moderate; multifocal vacuolation or sloughed/necrotic cells	Thin layer of cells (<5 cell layer thick)
4	50−75%	Marked; multifocal/segmental necrosis, epithelial loss/effacement	Thick layer of cells (>5 cell layer thick)
5	>75%	Severe; coalescing areas of necrosis, parenchymal effacement	Confluent areas of inflammation