Seasonal influenza
Based on CDC and WHO guidance, checked against those sources on Oct 12, 2026. Educational information only — not a diagnosis or a substitute for a licensed healthcare professional.
Common symptoms
- Fever or feeling feverish/chills (not everyone has a fever)
- Cough
- Sore throat
- Runny or stuffy nose
- Muscle or body aches
- Headache
- Tiredness
- Vomiting and diarrhea (more common in children)
Symptoms usually start 1–4 days after exposure, often suddenly. These symptoms can also be caused by other illnesses.
Seek emergency care for
- Difficulty breathing or shortness of breath
- Persistent pain or pressure in the chest or abdomen
- Persistent dizziness, confusion, or inability to wake up
- Seizures
- Not urinating
- Severe muscle pain, weakness or unsteadiness
- Fever or cough that improve but then return or worsen
- Worsening of chronic medical conditions
Emergency warning signs in children
- Fast breathing or trouble breathing
- Bluish lips or face
- Ribs pulling in with each breath
- Chest pain
- Severe muscle pain (child refuses to walk)
- Dehydration (no urine for 8 hours, dry mouth, no tears when crying)
- Not alert or interacting when awake
- Seizures
- Fever above 104°F (40°C) that does not come down with fever-reducing medicine, or any fever in a baby younger than 12 weeks
- Fever or cough that get better but then come back or get worse
- Chronic medical conditions getting worse
When to contact a healthcare professional
- Within the first 1–2 days of symptoms if you or the sick person is at higher risk (young child, 65+, pregnant, chronic condition, weakened immune system).
- If symptoms are severe or getting worse.
- If fever or cough improve but then return or get worse.