Flu is a common infectious viral illness spread by coughs and sneezes. It can be very unpleasant, but most people begin to feel better within about a week.
You can catch flu – short for influenza – all year round, but it's especially common in the winter season, which is why it's sometimes called "seasonal flu".
It's not the same as the common cold. Flu is caused by a different group of viruses and the symptoms tend to start more suddenly, be more severe and last longer. Flu can be very serious for some people.
Some of the main symptoms of flu include:
- a high temperature (fever) of 38C (100.4F) or above
- tiredness and weakness
- a headache
- general aches and pains
- a dry, chesty cough
Cold-like symptoms – such as a blocked or runny nose, sneezing, and a sore throat – can also be caused by flu, but they tend to be less severe than the other symptoms you have.
Flu can make you feel so exhausted and unwell that you have to stay in bed and rest until you feel better. Some people are more at risk to complications if they get flu than others, this includes the very young, the elderly, pregnant women and those with long term health conditions.
NHS Direct Wales has a cold and flu symptom checker that you can use.
Read more about the symptoms of flu.
What to do
If you're otherwise fit and healthy, there's usually no need to see a doctor if you have flu-like symptoms.
The best remedy is to rest at home, keep warm and drink plenty of water to avoid dehydration. You can take paracetamol or ibuprofen to lower a high temperature and relieve aches if necessary.
Flu spreads easily so stay off work or school until you're feeling better. For most people, this will take about a week.
Read more about treating flu at home.
When to see your GP
Consider visiting your GP if you :
- are 65 years of age or over
- are pregnant
- have a long-term medical condition – such as diabetes, heart disease, lung disease, kidney disease, liver disease, have had a stroke or mini stroke, or a neurological disease
- have a weakened immune system – for example, because you're having chemotherapy or have HIV
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.
Read more about antiviral medication for flu.
It is also important to visit your GP if:
How long does flu last and is it serious?
If you have flu, you generally start to feel ill within a few days of being infected.
You will probably begin to feel much better within a week or so, although you may feel tired for much longer.
You will usually be most infectious from the day your symptoms start and for a further three to seven days. Children and people with weaker immune systems may remain infectious for longer. Some people are infectious and have no symptoms.
Most people will make a full recovery and won't experience any further problems, but elderly people, the very young, pregnant women and people with certain long-term medical conditions are more likely to have a bad case of flu or develop a serious complication, such as a chest infection.
Read more about the complications of flu.
How you catch flu
The flu virus is contained in the millions of tiny droplets that come out of the nose and mouth when someone who is infected coughs or sneezes.
These droplets typically spread about one metre. They hang suspended in the air for a while before landing on surfaces, where the virus can survive for up to 24 hours.
Anyone who breathes in the droplets can catch flu. You can also catch the virus by touching the surfaces that the droplets have landed on if you pick up the virus on your hands and then touch your nose or mouth.
Everyday items at home and in public places can easily become contaminated with the flu virus, including food, door handles, remote controls, handrails, telephone handsets and computer keyboards. Therefore, it's important to wash your hands frequently.
You can catch flu many times, because flu viruses change regularly.
Preventing the spread of flu
The best way to prevent spreading flu is to have a flu vaccine, but you can also help reduce the chances of catching flu or spreading it to others with good hygiene measures.
Always wash your hands regularly with soap and warm water, as well as:
- regularly cleaning surfaces such as your computer keyboard, telephone and door handles to get rid of germs
- using tissues to cover your mouth and nose when you cough or sneeze
- putting used tissues in a bin as soon as possible
You can also help stop the spread of flu by avoiding unnecessary contact with other people while you're infectious. You should stay off work or school until you're feeling better.
People more at risk of serious illness if they catch flu, should have an annual flu vaccine (see below) and if they are exposed to flu antiviral medication may be recommended to help reduce the risk of becoming infected.
Read more about how to stop the spread of flu.
The flu vaccine
The following groups are eligible for free NHS flu vaccination:
- those aged 65 years and over
- those aged six months to under 65 years in clinical risk groups (see below)
- pregnant women
- adults who are morbidly obese (have a BMI of 40 or above)
- those who live in long-stay residential care homes
- all two and three year olds (age on 31 August 2016)
- all children in reception class and year 1, 2 and 3 in primary school.
An annual flu vaccine nasal spray is also now offered to children aged two
to seven years old. Two and three year olds will have their vaccine at the GP surgery, and four to seven years olds will have their vaccine in school.
People who are considered at clinical risk of flu include:
- chronic chest disease (including moderate to severe asthma)
- chronic heart disease
- chronic kidney disease
- chronic liver disease
- Chronic neurological disease (including stroke or mini stroke)
- Diabetes (including diet controlled)
- Poor immune system (due to a health condition or treatment)
- Poorly functioning spleen (or have had their spleen removed)
The best time to have the vaccine is in the autumn, before flu starts to circulate. You should have the flu vaccination every year so you stay protected, as the viruses that cause flu change every year.
For more information on who should have the flu jab and how to get it: