What is the recommended antiviral and supportive treatment regimen for an adult with confirmed or suspected H5N1 avian influenza, including dosing, alternatives for oral intolerance or resistance, and infection‑control precautions?

The recommended treatment for confirmed or suspected H5N1 avian influenza is prompt initiation of a neuraminidase‑inhibitor antiviral, ideally within 48 hours of symptom onset, together with supportive care and strict infection‑control precautions. For most adults the first‑line regimen is oseltamivir 150 mg orally twice daily for at least 5 days (the course can be extended to 10 days or longer for severe disease or delayed viral clearance). If the patient cannot tolerate oral medication, inhaled zanamivir 10 mg twice daily for 5 days, intravenous peramivir 600 mg once daily for 5 days, or a single oral dose of baloxavir (40 mg if <80 kg, 80 mg if ≥80 kg) are acceptable alternatives. In cases of known or suspected oseltamivir resistance, or in critically ill patients, combination therapy (e.g., high‑dose oseltamivir plus zanamivir) or switching to peramivir is reasonable. Supportive measures include aggressive hydration, antipyretics, oxygen supplementation, and, when indicated, mechanical ventilation and intensive‑care monitoring. Patients should be placed under droplet and contact isolation, and healthcare workers must use appropriate personal protective equipment. Close clinical monitoring for respiratory deterioration, secondary bacterial infection, and adverse drug effects is essential, and antiviral therapy should be continued for the full prescribed duration even if symptoms improve rapidly.