Pneumonia is an inflammation of the lungs. This usually occurs as a result of an infection caused by bacteria or viruses, or less commonly by fungi or parasites. It is normally spread by breathing in infected droplets. In rare cases, pneumonia can develop from an infection, when germs enter the lungs through your bloodstream.

Pneumonia can develop suddenly within 24 hours or may sometimes come on more slowly, over several days. A cough is a normal early sign along with shivering fits, fever, loss of appetite and pains in the chest. The cough usually produces phlegm.

Once the airways of the lungs become inflamed and fill with fluid, it becomes difficult to breathe. Breathing may become rapid and shallow.  Complications of pneumonia are more common in older people, however it can affect people of any age and can be more serious for babies and young children.

The information outlined above reflect current NHS Choices recommendations

Pneumonia can be serious and sometimes fatal.  The infection can spread to other parts of the body and result in blood poisoning (medically known as septicaemia).

Pneumonia is of greater risk to people who have other health conditions, such as a lung condition or a weakened immune system. People who smoke also put themselves at a greater risk of pneumonia. The immune system of those with HIV/AIDS is weakened and people suffering from chronic problems with their heart, liver or kidneys have an increased risk of pneumonia. Pneumonia is also a major complication of flu. 

There are two main types of pneumonia. If someone becomes infected while living at home, it is called ‘community-acquired pneumonia’. If it is contracted after 2-4 days in hospital, it is termed ‘hospital-acquired pneumonia’.

Pneumonia is most commonly caused by an infection, usually a bacterial infection although viruses can also be associated.  In adults, a bacterium called Streptococcus pneumoniae is the most likely cause. This form of pneumonia is sometimes called pneumococcal pneumonia.