Flu is a highly infectious illness that spreads rapidly through the coughs and sneezes of people who are carrying the virus.
If you're at risk of complications from flu, make sure you have your annual flu vaccine, available each year usually from October onwards.
There are two types of flu vaccine:
The effects of flu
Flu symptoms can hit quite suddenly and severely. They usually include fever, chills, headaches and aching muscles. You can often get a cough and sore throat.
Because flu is caused by a virus and not bacteria, antibiotics won't treat it.
Anyone can get flu, but it can be more serious for certain people, such as:
- People aged 65 or over
- People who have a serious medical condition
- Pregnant women
If you are in one of these groups, you're more vulnerable to the effects of flu (even if you're fit and healthy) and could develop flu complications, which are more serious illnesses such as bronchitis and pneumonia, which could result in hospitalisation.
Flu can also make existing medical conditions worse.
Read more about flu.