Pneumonia is caused by an infection in the lungs. The infection affects the air sacs in the lungs rather than the tubes that carry air to and from the lungs. Infected parts of the lung fill up with fluid, which contains white blood cells that fight the infection.

Last Update 10/06/2021
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What causes pneumonia? Where does it come from?

Who gets pneumonia?

Pneumonia is caused by germs (tiny organisms that can cause disease). Viruses, bacteria and fungi are types of germ that can cause pneumonia. Healthy people don’t usually have these germs in their lung tissue.

Germs sometimes get to the lung through our bloodstream, but most often they reach the lung tissue inside tiny droplets of water in the air that we breathe in. Usually, these germs come from other people, who spread them by coughing and sneezing out the droplets of water containing the germs.

Sometimes, the germs come from more unusual places. Legionnaires’ disease is a type of pneumonia caused by germs that thrive in very warm water. The germs that cause psittacosis are usually caught from birds, especially parrots. MRSA is often found in hospitals and can cause pneumonia in people who are admitted to hospital for other reasons.

Would I know if I had pneumonia?

Anyone can get pneumonia, even people who are fit and healthy. However, germs are more likely to Infect a person whose immunity is low and their natural defences are weakened. Very young and very old people have weaker lung defences, so pneumonia is more common early and late in life.

Some other things that can weaken these defences are tobacco smoke, viral infections that attack the breathing tubes (such as the common cold) and other viral infections (such as HIV). Some medicines, like those given for cancer therapy, also weaken the immune system, and a serious illness or an operation can make people more vulnerable. This is why patients sometimes develop pneumonia when they are already in hospital for another reason.

How would a doctor know if I had pneumonia?

If you had pneumonia you would certainly know you were ill, but you might not know you had pneumonia, as the symptoms can be confused with other illnesses. Common symptoms include:

  • cough, sometimes with yellow, green or blood-flecked phlegm
  • breathlessness
  • chest pain, which may get worse when you breathe in
  • a high temperature
  • shivery episodes
  • loss of appetite
  • weakness

How is pneumonia treated?

As well as asking about your symptoms, the doctor may be able to hear noises when he or she listens to the affected part of the lung with a stethoscope. The diagnosis is not easy to make, however, and often it is only confirmed when a chest X-ray shows that there is fluid in part of the lungs.

What should I do if I, or someone I care for, gets pneumonia?

Antibiotics are the main treatment for pneumonia. Most people will get better at home, but more severely ill people will have to go to hospital so that oxygen can be administered and fluids given in a drip. Although most people get better, if the pneumonia is very severe, people can die, even with the best treatment.

How quickly should I get better?

Can I do anything to prevent pneumonia?

Most symptoms, such as chest pain and fever, get better in a few days. The cough usually takes 2 or 3 weeks to go, but tiredness and weakness can take as long as 6 months to clear completely. If your symptoms do not get better as expected, or if the illness seems to come back, your doctor will want to look for any underlying reasons you may be particularly at risk of pneumonia.

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