Figure. Postmortem samples from clinically affected pigs, Argentina, 2009. A) Macroscopic lung lesions with distinctive scattered dark-red foci of lobular consolidation (chessboard-like) in all lobes. B) Severe necrotizing bronchiolitis with partially denuded epithelia. Hematoxylin-eosin stain; original magnification ×400. C) General view of the alveolar walls showing moderate interstitial thickening by leukocytes. Hematoxin-eosin stain; original magnification ×200. D) Bronchioli. Positive-labeled nuclei and cytoplasm of bronchial epithelial cells and mononuclear cells in the alveoli. 3,3′-diaminobenzidine counterstain with hematoxylin stain; original magnification ×200.