Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc
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In March and early April 2009, cases of a new swine-origin influenza A (H1N1) virus were diagnosed in Mexico and the United States. Influenza virus presents as a respiratory infection with high morbidity and mortality. We describe the postmortem findings of eight confirmed cases of influenza A/H1N1 in a medical examiner setting. ⋯ A wide range of histopathological findings including tracheitis, necrotizing bronchiolitis, alveolitis, intra-alveolar hemorrhage, and hyaline membranes, both in a focal and in a diffuse distribution, were identified. Influenza A/H1N1 viral infection presents with a wide range of histological findings in a diffuse or focal distribution; most consistently with tracheitis, necrotizing bronchiolitis, and alveolitis with extensive alveolar hemorrhage. These histopathological findings at autopsy along with a clinical history of flu-like symptoms should raise suspicion for influenza A/H1N1 infection, and postmortem analysis by the reverse transcription-polymerase chain reaction (RT-PCR) is recommended for an accurate diagnosis.