Pneumonia is swelling (inflammation) of the tissue in one or both lungs. It's usually caused by a bacterial infection.
At the end of the breathing tubes in your lungs are clusters of tiny air sacs. If you have pneumonia, these tiny sacs become inflamed and fill up with fluid.
The symptoms of pneumonia can develop suddenly over 24 to 48 hours, or they may come on more slowly over several days.
Common symptoms of pneumonia include:
Less common symptoms include:
See your GP if you feel unwell and you have typical symptoms of pneumonia.
Seek urgent medical attention if you're experiencing severe symptoms, such as rapid breathing, chest pain or confusion.
In the UK, pneumonia affects around 8 in 1,000 adults each year. It's more widespread in autumn and winter.
Pneumonia can affect people of any age, but it's more common – and can be more serious – in certain groups of people, such as the very young or the elderly.
People in these groups are more likely to need hospital treatment if they develop pneumonia.
Pneumonia is usually the result of a pneumococcal infection, caused by bacteria called Streptococcus pneumoniae.
Many different types of bacteria, including Haemophilus influenzae and Staphylococcus aureus, can also cause pneumonia, as well as viruses and, more rarely, fungi.
As well as bacterial pneumonia, other types include:
The following groups have an increased risk of developing pneumonia:
Your GP may be able to diagnose pneumonia by asking about your symptoms and examining your chest. Further tests may be needed in some cases.
To help make a diagnosis, your GP may ask you:
Your GP may also take your temperature and listen to your chest and back with a stethoscope to check for any crackling or rattling sounds.
They may also listen to your chest by tapping it. Lungs filled with fluid produce a different sound from normal healthy lungs.
If you have mild pneumonia, you probably won't need to have a chest X-ray or any other tests.
You may need a chest X-ray or other tests, such as a sputum (mucus) test or blood tests, if your symptoms haven't improved within 48 hours of starting treatment.
Mild pneumonia can usually be treated at home by:
If you don't have any other health problems, you should respond well to treatment and soon recover, although your cough may last for some time.
As pneumonia isn't usually passed from one person to another, it's safe to be around others, including family members.
However, people with a weakened immune system should avoid close contact with a person with pneumonia until they start to get better.
For at-risk groups, pneumonia can be severe and may need to be treated in hospital.
This is because it can lead to serious complications, which in some cases can be fatal, depending on a person's health and age.
Read more about treating pneumonia.
Complications of pneumonia are more common in young children, the elderly and those with pre-existing health conditions, such as diabetes.
Possible complications of pneumonia include:
You'll be admitted to hospital for treatment if you develop one of these complications.
Although most cases of pneumonia are bacterial and aren't passed on from one person to another, ensuring good standards of hygiene will help prevent germs spreading.
For example, you should:
A healthy lifestyle can also help prevent pneumonia. For example, you should avoid smoking as it damages your lungs and increases the chance of infection.
Find out how to stop smoking.
Excessive and prolonged alcohol misuse also weakens your lungs' natural defences against infections, making you more vulnerable to pneumonia.