Although most are mild and get better on their own, some can be serious or even life-threatening.
The main symptoms of a chest infection can include:
You may also experience more general symptoms of an infection, such as a headache, fatigue, sweating, loss of appetite, or joint and muscle pain.
Most bronchitis cases are caused by viruses, whereas most pneumonia cases are due to bacteria.
These infections are usually spread when an infected person coughs or sneezes. This launches tiny droplets of fluid containing the virus or bacteria into the air, where they can be breathed in by others.
The infections can also be spread to others if you cough or sneeze onto your hand, an object or a surface, and someone else shakes your hand or touches those surfaces before touching their mouth or nose.
Certain groups of people have a higher risk of developing serious chest infections, such as:
Read more about the causes of pneumonia.
Many chest infections aren't serious and get better within a few days or weeks. You won't usually need to see your GP, unless your symptoms suggest you have a more serious infection (see below).
While you recover at home, you can improve your symptoms by:
Avoid cough medicines, as there's little evidence they work, and coughing actually helps you clear the infection more quickly by getting rid of the phlegm from your lungs.
Antibiotics aren't recommended for many chest infections, because they only work if the infection is caused by bacteria, rather than a virus.
Your GP will usually only prescribe antibiotics if they think you have pneumonia, or you're at risk of complications such as fluid building up around the lungs (pleurisy).
If there's a flu outbreak in your local area and you're at risk of serious infection, your GP may also prescribe antiviral medication.
Read more about treating pneumonia.
You should see your GP if:
Your GP should be able to diagnose you based on your symptoms and by listening to your chest using a stethoscope (a medical instrument used to listen to the heart and lungs).
There are measures you can take to help reduce your risk of developing chest infections and stop them spreading to others.
If you smoke, one of the best things you can do to prevent a chest infection is to stop. Smoking damages your lungs and weakens your defences against infection.
Read more information and advice about stopping smoking.
Although chest infections generally aren't as contagious as other common infections, like flu, you can pass them on to others through coughing and sneezing.
Therefore, it's important to cover your mouth when you cough or sneeze, and to wash you hands regularly. Put tissues in the bin immediately.
Read more about preventing germs from spreading.
Excessive and prolonged alcohol misuse can weaken your lungs' natural defences against infections and make you more vulnerable to chest infections.
To keep your risk of alcohol-related harm low, the NHS recommends:
Regular or frequent drinking means drinking alcohol most weeks. The risk to your health is increased by drinking any amount of alcohol on a regular basis.
Eating a healthy, balanced diet can help strengthen the immune system, making you less vulnerable to developing chest infections.
If you're at an increased risk of chest infections, your GP may recommend being vaccinated against flu and pneumococcal infections (a bacterium that can cause pneumonia).
These vaccinations should help to reduce your chances of getting chest infections in the future.
Flu and pneumococcal vaccinations are usually recommended for: