Influenza (Flu)

Influenza (flu) is a contagious respiratory illness caused by influenza viruses that typically comes on suddenly and is characterized by fever, chills, severe body aches, headache, fatigue, cough, sore throat, and nasal congestion — distinct from a cold by its abrupt onset and systemic symptoms. It spreads through respiratory droplets and is contagious from one day before symptoms appear through 5–7 days after onset, making early isolation and hand hygiene essential to prevent spread. Antiviral medications are most effective when started within 48 hours of symptom onset and are especially important for high-risk patients including adults 65 and older, pregnant women, and people with asthma, diabetes, heart disease, or immunocompromised conditions. Treatment also includes rest, adequate hydration, and OTC medications for fever and body aches as needed. Most healthy adults recover fully within 7–14 days, though fatigue and cough can linger for several weeks after other symptoms resolve. Seek emergency care immediately if you develop difficulty breathing, persistent chest pain, confusion, inability to stay awake, bluish or grayish lips or fingernails, or symptoms that improve then suddenly return with worsening fever and cough, as these may indicate serious complications including pneumonia.