Influenza, or flu, is a contagious respiratory infection caused by influenza viruses. It usually begins suddenly and is more intense than a common cold. Most people recover within about a week, although cough and fatigue may last longer.
Symptoms
Typical symptoms include fever or chills, dry cough, sore throat, headache, marked tiredness and muscle or joint aches. Children may also have nausea, vomiting or diarrhoea. Flu can worsen asthma and other long-term conditions.
Self-care and treatment
Rest, drink enough fluid and use suitable pain or fever medicine. Stay away from others while feverish or too unwell for normal activities, cover coughs and wash hands. Antibiotics do not treat influenza. Antiviral medicines may reduce complications when started early, especially for people at higher risk or with severe illness.
Prevention
Seasonal vaccination is the best protection against severe influenza and is updated because circulating viruses change. Ventilation, hand hygiene and avoiding close contact when ill also reduce spread.
When to seek medical advice
Seek early advice if you are pregnant, very young or older, immunocompromised, have significant heart, lung, kidney, neurological disease or diabetes, or symptoms are severe or worsening. A cough that persists may have another cause such as acute bronchitis.
Emergency signs
Call emergency services for severe breathing difficulty, blue or grey lips, persistent chest pain, confusion, seizure, collapse, inability to wake or signs of severe dehydration. Urgent review is also needed when fever or cough improves and then returns worse.
Sources
Reviewed: 28 August 2026