Lung pathology in 2009 pandemic H1N1 influenza

From the American Journal of Respiratory and Critical Care Medicine:

AT A GLANCE COMMENTARY
Scientific Knowledge on the Subject
Most patients with H1N1 infection present flulike symptoms with a benign course. Patients with comorbidities may have a serious clinical presentation with respiratory failure. The main cause of death is acute respiratory distress syndrome. The pulmonary pathology of patients who died with the H1N1 infection is incompletely described.

What This Study Adds to the Field
This study shows that the main pathological changes associated with H1N1 infection are localized to the lungs, where three distinct histological patterns can be identified: diffuse alveolar damage (DAD), necrotizing bronchiolitis, and DAD with intense alveolar hemorrhage. There is also evidence of ongoing pulmonary aberrant immune response.