What is pneumonia?

Pneumonia is caused by infection from bacteria, viruses or fungi, which irritates the lungs and causes them to become inflamed and swell up with fluid.¹

The most common cause of bacterial pneumonia is a pneumococcal infection, due to bacteria called Streptococcus pneumoniae.^{​​​​​​​1} It can be spread from person to person through physical contact, coughing and sneezing.² If someone has pneumonia, try to avoid contact with them.

Pneumonia symptoms can be mistaken for a cold or flu

Pneumonia can make you feel really unwell.² As the symptoms of pneumonia vary and are similar to those of cold and flu, many people may not realise that they have pneumonia until they visit a health care professional.²