Lung tissue was collected, fixed in 10% neutral buffered formalin, and submitted to the Cornell University Animal Health Diagnostic Center for sectioning and staining. Tissue sections (4 μm) were stained with H&E and examined by a board-certified veterinary anatomic pathologist blinded to group categories. Lung pathology was scored based on the percentage of each feature affected across the entire lung section. The features scored were perivascular infiltrates, interstitial infiltrates, presence of cells in alveoli lumina, and type II pneumocyte hyperplasia, the presence of sloughed or necrotic cells in bronchiolar lumina. Each point corresponded to the amount of tissue affected: normal (0); less than 10% (1 ); between 10 and 25% (2 ); 26 to 50% (3 (link)); and higher than 50% (4 (link)). As described previously, IHC was performed on lung tissue with an anti–SARS-CoV-2 nucleoprotein antibody (GeneTex: GTX635679) at a 1:5000 dilution (58 (link)).