Flu is an illness caused by the influenza virus. It occurs every year, usually in winter. It is important that you protect yourself and others from flu by helping to prevent the spread of the virus and getting the flu vaccine if you are eligible.
You can catch flu – short for influenza – all year round.
It's especially common in winter, which is why it's also known as ‘seasonal flu’.
It usually peaks between December and March.
It's not the same as the common cold.
Flu is caused by a different group of viruses. The symptoms tend to be more severe and last longer.
Symptoms of flu
The symptoms of flu include:
- fever (typically 38–40°C) - this tends to be more severe in children
- fatigue/unusual tiredness
- runny nose
- sore throat
- shortness of breath or a cough
- loss of appetite
- aching muscles
- vomiting or diarrhoea
- sensitivity to light
- dry, unproductive cough
Flu symptoms usually peak after two or three days and you should begin to feel much better within five to eight days.
However, older people or those with certain medical conditions may develop complications that can lead to serious illness and can be life-threatening.
That is why it is important to get the seasonal flu vaccine if it is offered to you.
Telling the difference between cold and flu
Cold and flu symptoms are similar but flu tends to be more severe.
- appear gradually
- affects mainly your nose and throat
- makes you feel unwell, but you're OK to carry on as normal (for example, go to work)
- appear quickly within a few hours
- affect more than just your nose and throat
- makes you feel exhausted and too unwell to carry on as normal
What to do if you have flu
For most people, flu is a mild illness that can be treated at home with rest, drinking plenty of fluids and taking medicine, such as paracetamol, as directed to control the symptoms.
You should not go to an emergency department unless it is urgent and essential.
When to see your GP
- you're 65 years of age or over
- you're pregnant
- you have a long-term medical condition – such as diabetes, lung disease, kidney disease or a neurological disease
- you have a weakened immune system – for example, because you're having chemotherapy or have HIV
- you develop chest pain, shortness of breath or difficulty breathing, or start coughing up blood
- your symptoms are getting worse over time or haven't improved after a week
In these situations, you may need medication to treat or prevent complications of flu.
Your doctor may recommend taking antiviral medicine to reduce your symptoms and help you recover more quickly.
How flu is spread
The flu virus is spread in the small droplets of saliva coughed or sneezed into the air by an infected person.
If you inhale these droplets, you may become infected.
Flu can also spread if someone infected with the virus touches:
- common surfaces such as door handles with unwashed hands
- the hand of someone else without washing their hands first
Preventing the spread of the flu virus
You can take simple steps to help stop the spread of the flu virus. You should always:
- carry tissues
- use tissues to cover your mouth and nose when you cough or sneeze
- dispose of the dirty tissues quickly
- wash your hands regularly
More useful links
- Reducing the spread of Coronavirus (COVID-19) and other respiratory infections
- How to use your health services
- Flu is more serious than you think (leaflet and translations)
- Flu is more serious than you think: pregnant women (leaflet and translations)
- Hand hygiene
The information on this page has been adapted from original content from the NHS website.
For further information see terms and conditions.