Snapshot A 50-year-old man presents to the emergency room for altered mental status, high fevers, chills, muscles aches, and headaches for 1 week. He was diagnosed with flu at an urgent care center but declined oseltamivir at the time. He had been improving until 2 days ago, when he started having fevers and chills again along with a productive cough. On physical exam, his oxygen saturation is at 90% on room air and is put on supplemental oxygen. Infectious workup, including blood cultures, are pending. A chest radiograph shows a right lower lung consolidation, and he is started on empiric antibiotics. Introduction Classification login to view 4 more bullets Prevention login to view 5 more bullets Epidemiology Incidence login to view 1 more bullet Demographics login to view 1 more bullet Risk factors login to view 5 more bullets Etiology Influenza A and B are causes of seasonal epidemics Can originate from animal strains login to view 2 more bullets Pathogenesis login to view 3 more bullets Presentation Symptoms login to view 6 more bullets Physical exam login to view 1 more bullet Imaging Chest radiography login to view 5 more bullets Studies Labs login to view 3 more bullets Differential Upper respiratory infection login to view 2 more bullets DIAGNOSIS Making the diagnosis login to view 1 more bullet Treatment Management approach login to view 3 more bullets Conservative login to view 6 more bullets Medical login to view 4 more bullets Complications Secondary bacterial infection Myositis or myocarditis Central nervous system involvement Prognosis May lead to severe bacterial superinfections login to view 1 more bullet May be fatal