Infections (whole body)Viral infectionICD-10 J11
Influenza (flu)
Also called: Flu
A contagious respiratory virus causing sudden fever, aches and cough. Most recover in a week, but it can be severe in older people, pregnancy and chronic illness.
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Causes
- Influenza A and B viruses
Risk factors
- Age over 65
- Pregnancy
- Chronic heart, lung, kidney disease, diabetes
- Weakened immunity
Symptoms
- Sudden fever
- Muscle aches
- Exhaustion
- Dry cough, sore throat
- Headache
Diagnosis — tests and examinations
- Clinical during flu season; PCR testing
Treatment
Medicines and medical treatment
- Antivirals (oseltamivir, baloxavir) for high-risk or severe cases, best within 48 hours
- Paracetamol or ibuprofen
Self-care, home remedies and lifestyle
- Rest, fluids, stay home
Possible complications
- Pneumonia
- Myocarditis
- Worsening of chronic illness
Prevention
- Annual flu vaccination
- Hand hygiene, covering coughs
Outlook
Recovery in 1–2 weeks for most.
When to see a doctor
Seek care for breathlessness, chest pain, confusion or if you are at high risk.
Sources and further reading
These sources cover this condition. They have not been checked against every statement on this page.
Related conditions
Educational overview, not medical advice. Treatment varies by person and location. Consult a qualified health professional for diagnosis or care. Read our content and model notes and privacy information.