Is pneumonia contagious?

Pneumonia is most commonly caused by bacteria and viruses, which are contagious. It can also be caused by breathing in a foreign object (aspiration pneumonia), and in rare cases a fungal infection, which is not usually contagious.

Causes of pneumonia 

Bacterial pneumonia

Pneumonia is inflammation (swelling) of the tissue in one or both of your lungs. It’s usually caused by an infection. The most common cause of pneumonia in adults is a bacterium called Streptococcus pneumoniae. Other types of bacteria that can cause pneumonia include:

  • Haemophilus influenzae 
  • Staphylococcus aureus
  • Mycoplasma pneumoniae (outbreaks tend to occur every four to seven years, more commonly in children and young people)

Read more information about other bacteria that can cause 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.

Fungal pneumonia

In the UK, pneumonia caused by fungal infection of the lungs is rare in people who are normally healthy. Pneumocystis jirovecii pneumonia remains the most common fungal pneumonia in people with low immune systems, such as those infected with HIV.

Aspiration pneumonia

Pneumonia can also be caused by breathing in a foreign object, such as a piece of food, or a harmful substance, such as smoke. This is called aspiration pneumonia. If breathing in a foreign object leads to a bacterial infection, this is contagious.

Catching pneumonia

The germs that can cause pneumonia are usually breathed in. People often have small amounts of germs in their nose and throat that can be passed on through:

  • coughs and sneezes: these launch tiny droplets of fluid containing germs into the air, which someone else can breathe in  
  • touching an object and transferring germs onto it: someone else can touch this object, and then touch their own mouth or nose

Streptococcus pneumoniae bacteria, which causes most cases of pneumonia, is far less contagious than a cold or flu. This is because most people’s immune systems can kill the bacteria before they have the opportunity to cause an infection.

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

Vaccination

Some people are at higher risk of developing pneumonia. To help protect against pneumonia, it’s recommended that people at higher risk of complications, such as those who are 65 or over, should have:

Good hygiene

You can help prevent the spread of germs by practising good hygiene. For example:

  • wash your hands regularly and thoroughly, particularly after touching your mouth and nose and before handling food 
  • cough and sneeze into a tissue, then throw it away immediately and wash your hands 
  • don’t share cups or kitchen utensils with others

Read the answers to more questions about winter health.

Further information:

Page last reviewed: 26/09/2012

Next review due: 26/09/2014