Fatal coinfection with Oropouche virus and influenza A(H1N1)pdm09: Case report and post-mortem findings.

Oropouche virus (OROV) is an emerging orthobunyavirus that causes increasingly severe and deadly disease in Brazil. However, coinfection with influenza A(H1N1)pdm09 has not been previously described in the published literature, to our knowledge. We report the first documented fatal case of OROV and influenza A(H1N1)pdm09 coinfection in a previously healthy 16-year-old female from rural Maranhão, Brazil. The patient presented with dyspnea, odynophagia, and hemoptysis and deteriorated rapidly, requiring orotracheal intubation on day three of illness due to massive endobronchial hemorrhage, followed by fatal hemodynamic collapse. Autopsy revealed bilateral serosanguineous pleural effusion, diffuse alveolar hemorrhage, pericardial petechiae, acute tubular necrosis, and cerebral edema with tonsillar herniation. Real-time reverse-transcriptase polymerase chain reaction confirmed OROV in lung, liver, spleen, and lymph node tissues, and influenza A(H1N1)pdm09 in both nasal swab and lung tissue; all other arboviruses and respiratory pathogens tested negative. The histopathological findings provide, to our knowledge, the first histopathological characterization of OROV-associated microvascular injury and suggest synergistic thromboinflammatory pathways with influenza A. This case broadens the recognized clinical spectrum of OROV and highlights the need for systematic coinfection screening and coagulation monitoring in severe arboviral presentations, even in young patients without comorbidities.