Common symptoms
Sudden fever
Rapid onset of high temperature, often above 101°F
Body aches
Widespread muscle pain and soreness that can be severe
Fatigue
Profound tiredness and weakness that may last days after other symptoms resolve
Cough
Dry cough that may worsen over the first few days of illness
Sore throat
Scratchy or painful throat accompanying other flu symptoms
Headache
Intense headache, often present from early in the illness
Influenza (flu) strikes suddenly and tends to be more severe than the common cold. It spreads through respiratory droplets and is most dangerous for young children, the elderly, pregnant women, and those with chronic health conditions.
The most intense symptoms — fever, body aches, and fatigue — typically peak within the first two to three days. Antiviral medications such as oseltamivir (Tamiflu) are most effective when started within 48 hours of symptom onset.
After the fever resolves, cough and fatigue may persist for another week or two. Returning to normal activity gradually is advised. Staying home prevents spreading the virus to others.