(b) Hematoxylin and eosin (H&amp;amp;E)-stained lung sections from mice infected with PR8 virus on day 2. Arrows indicate cellular infiltrates and necrotic debris occluding the airways. Original magnification, ×40. (c) Disease severity ('lung score') and extent of cell death (necrosis score) on day 2 after infection based on analysis of H&amp;amp;E-stained lung sections. (d) Necrosis score on day 7, estimated visually from H&amp;amp;E-stained lung sections, and flow cytometry analysis for annexin V-stained lung cell populations. 