Table 1.

Semiquantitative histopathological scoring criteria for the lungs of hamsters challenged with SARS-CoV-2

General evaluation	assessment percentage of lung damage area under 4× objective lens	0, none 1, focal lung inflammation within one lobe or <30% of the total lung section 2, diffuse lung inflammation within one lobe or involving 30–70% of the total lung section 3, diffuse lung inflammation involving more than one lobe or 70% of the total lung section
Bronchioles	assessing appearance and severity of peribronchiolar infiltration, intrabronchial wall infiltration, and bronchiolar epithelial cell death/desquamation	0, none 1, peribronchiolar infiltration 2, bronchiolar epithelial cell death 3, bronchiolar wall infiltration and/or severe epithelium desquamation
Alveoli	assessing the appearance, scope involved, and severity of alveolar septal infiltration, alveolar space infiltration, and alveolar space exudation	0, none 1, only alveolar wall thickening 2, focal area alveolar space infiltration, exudation involving <30% of lung section 3, diffuse alveolar space
Severity of vasculature inflammation	assessing the percentage of vessels affected	0, none 1, only perivascular edema and/or perivascular infiltration 2, mild infiltration within the vessel wall without endothelium infiltration 3, intensive infiltration into the smooth muscle or infiltration beneath the endothelium
Endothelialitis	presence of inflammatory cells beneath or within the endothelial cell layer	0, absent 1, rare 2, common
Endothelial hyperplasia	endothelial cells bulging into the lumen	0, absent 1, rare 2, common
Vasculitis	vessel walls infiltrated with inflammatory cells	0, absent 1, rare 2, common
Mural vascular wall degeneration	hypereosinophilic areas with loss of cell detail	0, absent 1, rare 2, common
Perivascular assessment	perivascular edema or inflammation	0, absent 1, rare 2, common
Repair	tissue repair	0, absent 1, hyperplasia 2, pneumocyte type 2 hyperplasia 3, fibrosis or granulation tissue

Total score = sum of all scores of individual category assessments for each lung section. There were five sections representing different lung lobes. The maximum score possible was 25 × 5 = 125.