Influenza Infection

Influenza can begin as an uncomplicated febrile respiratory illness and then deteriorate when viral injury, inflammation, or a secondary bacterial infection impairs gas exchange. The bedside pattern is usually abrupt fever, cough, marked myalgia, headache, and fatigue. The priority is not the temperature alone; it is the patient's oxygenation, work of breathing, mental status, hydration, and risk for complications. For REx-PN questions, link three decisions: recognize the syndrome, identify who needs testing or prompt antiviral therapy, and notice the change that makes the illness dangerous. Antivirals provide the greatest benefit when started within 48 hours, but a late presentation is not a reason to withhold treatment from a high-risk, hospitalized, or severely ill patient.