Which histologic findings are characteristic of influenza (H1N1) and avian (H5N1) influenza pneumonias?

Updated: Mar 24, 2021
  • Author: Zab Mosenifar, MD, FACP, FCCP; Chief Editor: John J Oppenheimer, MD  more...
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Influenza histopathology of lung tissue reveals edema, focal hemorrhages, and cellular infiltration. Alveoli may be denuded of epithelium, and intra-alveolar hemorrhage is common. The presence of an acellular hyaline membrane lining the alveoli is typical of influenza pneumonia.

Avian influenza (H5N1) typically shows fulminant, necrotizing, diffuse alveolar damage with patchy, interstitial, paucicellular fibrosis. (H1N1 pneumonia has shown diffuse alveolar damage, thick hyaline membranes, and prominent fibroblast proliferation.)

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