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Pneumonia is inflammation (swelling) of the tissue in one or both of your lungs. It is usually caused by an infection.

At the end of the airways in your lungs, there are clusters of tiny air sacs. If you have pneumonia, these tiny sacs become inflamed and fill up with fluid.

As well as making you cough, the inflammation makes it harder for you to breathe. It also means your body is less able to absorb oxygen. For more information, see Pneumonia - symptoms.

Terms such as bronchopneumonia, lobar pneumonia and double pneumonia are sometimes used, but refer to the same condition with the same causes and treatment.

How common is pneumonia?

In the UK, pneumonia affects up to 11 in 1,000 adults each year. It is more common during autumn and winter.

Pneumonia can affect people of any age. However, in some groups of people, it is more common and can be more serious. For example:

  • babies, young children and elderly people
  • people who smoke
  • people with other health conditions, such as a lung condition or a weakened immune system

For more information, see People at risk.

People in these groups are also more likely to need treatment in hospital.


Some forms of pneumonia can be more severe than others, depending on the cause.

Mild pneumonia can usually be treated at home with antibiotics (see Pneumonia - treatment). People who are otherwise healthy usually recover well. However, complications can still develop.

For people with other health conditions, pneumonia can be severe and may need to be treated in hospital.

This is because there are a number of complications that can accompany pneumonia, some of which can be fatal, depending on the health and age of the patient. These include respiratory failure, (when the lungs cannot take in enough oxygen) due to the air sacs filling with water, as well as lung abscesses and septicaemia. For more information see Pneumonia - complications.

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Pneumonia symptoms vary and can be similar to those of other chest infections, such as acute bronchitis.  

Symptoms can develop suddenly, for example, over 24-48 hours. However, they can also come on more slowly, over several days.

Common symptoms of pneumonia

If you have pneumonia, you are likely to have a cough. This may be dry, or you may produce phlegm (thick mucus) that is yellow, green, brownish or blood-stained.

Other common symptoms can include:

  • difficulty breathing: your breathing may be rapid and shallow. And you may feel breathless, even when you are resting
  • rapid heartbeat
  • fever
  • feeling generally unwell
  • sweating and shivering
  • loss of appetite
  • pain in your chest

Less common symptoms

Less commonly, symptoms of pneumonia can include:

  • coughing up blood (haemoptysis)
  • headaches
  • fatigue
  • nausea
  • vomiting
  • wheezing
  • pain in your joints and muscles
  • feeling confused and disorientated (particularly in elderly people)
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Pneumonia is most commonly caused by an infection, usually a bacterial infection.

However, many different bacteria, viruses and (rarely) fungi cause pneumonia; the germ depends on where the pneumonia began. For example, the germs that cause pneumonia caught in hospitals are different to those that cause pneumonia caught in the community.

People at risk

Some groups of people have a higher risk of developing pneumonia. For example:

  • babies and very young children
  • elderly people
  • people who smoke
  • people with other health conditions
  • people with a weakened immune system

Other health conditions that increase the risk of pneumonia developing include:

  • another lung condition such as asthma or cystic fibrosis
  • a heart condition
  • a kidney or liver condition
  • a lowered immune system

Your immune system can be weakened due to:

  • a recent illness such as flu
  • treatment for cancer, such as chemotherapy
  • medicines that suppress the immune system after an organ transplant
  • HIV or AIDS

Bacterial pneumonia

The most common cause of pneumonia in adults is a bacterium called Streptococcus pneumoniae. This form of pneumonia is sometimes called pneumococcal pneumonia.

Less commonly, other types of bacteria can cause pneumonia, including:

  • haemophilus influenzae
  • staphylococcus aureus
  • mycoplasma pneumoniae - outbreaks tend to occur every 4-7 years, more commonly in children and young people,

And rarely, the following bacteria can cause pneumonia:

  • Chlamydophila psittaci: this causes a rare form of pneumonia called psittacosis, which can be passed on to people from infected birds such as parrots, parakeets, pigeons, canaries and budgies (this condition is also called parrot fever or parrot disease)
  • Chlamydophila pneumoniae
  • Legionella pneumophila - Legionnaires' disease, an uncommon form of pneumonia.

Viral pneumonia

Viruses can also cause pneumonia, most commonly the respiratory syncytial virus (RSV), and sometimes the flu (influenza) type A or B virus.

Viruses are a common cause of pneumonia in young children.

Aspiration pneumonia

Rarely, pneumonia can be caused by breathing in (inhaling):

  • vomit
  • a foreign object, such as a peanut
  • a harmful substance, such as smoke or a chemical

The object or substance inhaled causes irritation in the lungs or damages them. This is called aspiration pneumonia.

Fungal pneumonia

In the UK, pneumonia caused by fungal infection of the lungs is rare in people who are normally healthy. It more often affects people whose immune systems are lowered (see  People at risk above).

Fungal pneumonia can rarely affect people who travel to places where these infections are more commonly found. For example, some parts of the USA, Mexico, South America and Africa.

The medical names for fungal pneumonia include histoplasmosis, coccidioidomycosis and blastomycosis.

How a lung infection happens

The germs that cause an infection are usually breathed in.

Rarely, pneumonia can develop from an infection somewhere else in your body, when the germs enter your lungs through your bloodstream.

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To make a diagnosis, your doctor may ask you:

  • whether you are breathing faster than usual
  • if you feel breathless
  • how long you have had your cough
  • whether you are coughing up sputum and what colour it is
  • if the pain in your chest is worse when you breathe in or out

Your doctor will probably take your temperature and listen to the back and front of your chest with a stethoscope, to check for any crackling or rattling sounds.

They may also listen to your chest by tapping it - if the lungs are filled with fluid, this produces a different sound to normal, healthy lungs.

Your blood pressure may be checked as well.

Most people with mild pneumonia do not need to have a chest X-ray or other tests.

A precise diagnosis is sometimes difficult to make, especially outside hospital, where chest X-rays are not immediately available. Other conditions such as the common cold, acute bronchitis and asthma share many of the same symptoms as pneumonia.

Chest X-ray and other tests

Your GP may arrange a chest X-ray or other tests if your symptoms have not started to improve within 48 hours of starting treatment.

A chest X-ray can show how much your lungs are affected. It can also help the doctor to distinguish between pneumonia and other chest infections, such as bronchitis.

Other tests your GP may arrange can include:

  • a sputum test
  • blood tests

Analysing samples of sputum or blood can help identify the bacterium or virus causing the infection.

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Treating pneumonia at home

Mild pneumonia can usually be treated with antibiotics at home.  Bacterial infection is the most common cause.

Antibiotic treatment usually works. You may continue to cough for two to three weeks after you finish the antibiotics and you may feel tired for even longer as your body continues to recover.

You should let your GP know if your symptoms do not start to get better within two days of starting treatment. For example, your symptoms may not have improved because:

  • The bacteria causing the infection may be resistant to the antibiotics. Your doctor may change to a different antibiotic, or they may start treatment with a second antibiotic while you continue to take the first one.
  • A virus may be causing the infection, rather than bacteria. Antibiotics have no effect on viruses. Your body's immune system will fight the viral infection by creating antibodies to it.

Sometimes, you may need hospital treatment, for example, if your symptoms are severe. See Pneumonia complications section for more information.


The steps below may help you to ease your symptoms.

Take painkillers such as paracetamol or ibuprofen to relieve any pain and reduce a fever. You should not take ibuprofen if you:

  • are allergic to aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs)
  • have asthma, kidney disease, a history of stomach ulcers or indigestion

Cough medicines are not recommended. Coughing enables you to clear mucus from your lungs, so trying to stop your cough could make the infection last longer. Also, there is little evidence that cough medicines are effective. A warm drink of honey and lemon can help relieve the discomfort caused by coughing.

Drink plenty of fluids to avoid dehydration and get plenty of rest to help your body recover.

If you smoke, it is more important than ever to stop, as smoking damages your lungs.

Once your symptoms improve, it may take some time for you to recover fully. For example, coughing may continue for some time. Speak with your GP if you are concerned.

After treatment

Your GP will probably ask to see you again around six weeks after you started your antibiotics.

In some cases, they may arrange follow-up tests, such as a chest X-ray. For example, if:

  • your symptoms have not improved
  • your symptoms have come back
  • you smoke
  • you are over the age of 50

Some people may be advised to have vaccinations against flu or pneumococcal infections after recovering from pneumonia. See the 'prevention' section for more information.

Aspiration pneumonia

If you have breathed in (inhaled) an object that is causing pneumonia, it may need to be removed.

The doctor may do this by using a tube to look into the airways in your lungs and then removing the inhaled object. This is called a bronchoscopy.

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Pneumonia can develop, for example:

  • as a complication of other serious health conditions, such as cancer
  • as a secondary bacterial infection after a viral condition such as flu
  • after surgery or an injury, particularly to the chest area, which makes you less able to breathe or cough fully, giving mucus the chance to build up

If you get repeated pneumonia infections, this may be a sign of other health problems, such as an existing lung condition or a weakened immune system.


Sometimes people can have bronchitis (inflammation of the air tubes in your lungs) at the same time as pneumonia. This is called bronchopneumonia. For more information, see the topic on bronchitis

Pleurisy, pleuritic pain and pleural effusion

Pleurisy is when the two thin linings between your lungs and your ribcage (the bones in your chest) become inflamed. It can be caused by lung conditions such as pneumonia. For more information, see the topic on pleurisy.

Sometimes, symptoms of severe pneumonia can include pleuritic pain - a sharp, stabbing pain in your chest in one place when you breathe in. This can also be a symptom of pleurisy.

Less commonly, fluid can build up in the space between your lungs and the wall of your chest.  This is called a pleural effusion. If this fluid becomes infected (empyema), it will usually be drained using a needle or thin tube.

Other complications

Other complications of pneumonia can include:

Blood infections can make you very ill and are normally treated in hospital.

Rarely, pneumococcal pneumonia can cause infection of the membranes covering the brain (pneumococcal meningitis).

People with weakened immune systems, for example, due to HIV or AIDS, sometimes develop a form of pneumonia called pneumocystis pneumonia. This is caused by a fungus called pneumocystis jirovecii (formerly pneumocystis carinii).

Treatment in hospital

In young children or people over the age of 65, pneumonia may need to be treated in hospital.

You may also need hospital treatment if:

  • your symptoms are more severe
  • your symptoms do not improve
  • you have an existing lung condition, such as cystic fibrosis

If you are admitted to hospital, you may have a chest X-ray or other tests, to help diagnose the condition and determine how severe it is.

If the level of oxygen in your blood is low (hypoxia), you may need extra oxygen. This can be given using a face mask. In severe cases, it may be necessary to use a ventilator (artificial breathing machine).

You may also be given fluids or antibiotics through a drip.

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To help protect against pneumonia, people in higher risk groups should be vaccinated. The recommended vaccinations are:

  • the pneumonia jab (pneumococcal polysaccharide vaccine - PPV) which protects against pneumococcal infections, and
  • the flu jab (influenza immunisation).

Healthy lifestyle

It is impossible to avoid bacteria and germs, but living a healthy lifestyle, by eating a healthy, balanced diet and taking regular exercise, will help you to be healthy.

Some lifestyle factors can increase your risk of developing pneumonia. For example:

  • smoking
  • alcohol abuse
  • intravenous drug abuse

Smoking damages your lungs. This means they can become infected more easily.

If you smoke, the best thing you can do to prevent pneumonia is to quit smoking.

To help you quit, call the NHS Smoking Helpline on 0800 169 0 169 for advice and support. For more information, visit the NHS Smokefree website. Your GP or pharmacist can also give you help and advice about quitting smoking.

Good hygiene

You can help to stop germs spreading to other people by practising good hygiene. For example:

  • When you cough or sneeze, cover your nose and mouth with a tissue, to catch the germs.
  • Throw used tissues away immediately, in a bin or toilet. Germs can live several hours after they leave your nose or mouth.
  • Wash your hands regularly to avoid transferring germs to anyone else or other objects.
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