Fig. 4. Lung pathology in ferrets inoculated with one of the four European swine influenza viruses and euthanized 5 days p.i. Lung tissue from ferrets, haematoxylin/eosin; bar, 50 µm. (a) Normal lung tissue from control ferret. (b) Ferret inoculated with H3N2, 5 days p.i. Suppurative bronchiolitis, dysplasia of bronchiolar epithelium and hyperplasia of BALT (asterisk). (c) Ferret inoculated with H1pdmN2sw, 5 days p.i. Suppurative bronchiolitis, dysplasia and desquamation (arrowhead) of bronchiolar epithelium and BALT hyperplasia (asterisk). (d) Ferret inoculated with H1N2, 5 days p.i. Suppurative bronchiolitis and peribronchiolar infiltration of mononuclear cells. Dysplasia, necrosis and desquamation (arrowhead) of bronchiolar epithelium. (e) Ferret inoculated with H1avN2hu, 5 days p.i. Suppurative bronchiolitis, and dysplasia, necrosis and desquamation (arrowhead) of bronchiolar epithelium.