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Updated: May 24, 2026

Modeling Dysplastic and Functional Lung Alveolar Repair after Influenza Infection
Published on: September 19, 2025
[Pulmonary pathology in fatal human influenza A (H1N1) infection]
Xue-jing Duan1, Yong Li, En-cong Gong
1Department of Pathology, Capital Medical University, Beijing, China.
Objective:
To study the pulmonary pathology in patients died of fatal human influenza A(H1N1) infection.
Methods:
Eight cases of fatal human influenza A (H1N1) infection, including 2 autopsy cases and 6 paramortem needle puncture biopsies, were enrolled into the study. Histologic examination, immunohistochemitry, flow cytometry and Western blotting were carried out.
Results:
The major pathologic changes included necrotizing bronchiolitis with surrounding inflammation, diffuse alveolar damage and pulmonary hemorrhage. Influenza viral antigen expression was detected in the lung tissue by Western blotting. Immunohistochemical study demonstrated the presence of nuclear protein and hemagglutinin virus antigens in parts of trachea, bronchial epithelium and glands, alveolar epithelium, macrophages and endothelium. Flow cytometry showed that the apoptotic rate of type II pneumocytes (32.15%, 78.15%) was significantly higher than that of the controls (1.93%, 3.77%).
Conclusion:
Necrotizing bronchiolitis, diffuse alveolar damage and pulmonary hemorrhage followed by pulmonary fibrosis in late stage are the major pathologic changes in fatal human influenza A (H1N1) infection.
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