Bronchiolitis

Bronchiolitis is a common lower respiratory tract infection that affects babies and young children. The early symptoms are similar to those of a common cold, such as a runny nose and cough. As bronchiolitis develops, it can cause:

• a slight fever (raised temperature)
• a dry and persistent cough
• difficulty feeding

Bronchiolitis is most commonly caused by an airborne virus known as the respiratory syncytial virus (RSV). This causes the smallest airways in the lungs (the bronchioles) to become infected and inflamed (swollen). The inflammation reduces the amount of air entering the lungs, making it more difficult for the child to breathe.

How common in bronchiolitis?

It is estimated that one-third of infants in the UK develop bronchiolitis in the first year of their life.  The condition is most common in infants who are three to six months old. By two years of age, almost all infants have been infected with RSV and 40-50% will have had bronchiolitis.  

Most cases of bronchiolitis occur during the winter months, from November to March, when the viruses that can cause bronchiolitis are more common. It is also possible to get bronchiolitis more than once during the same winter season. 

Outlook

There is no medication to kill the viruses that cause bronchiolitis, but the infection usually clears up within two weeks without any treatment. Most infants can be cared for at home by ensuring they get enough fluid and by monitoring their condition.

Around 3% of infants who are under one year of age and have bronchiolitis will need to be admitted to hospital. This is because they develop more serious symptoms, such as difficulty breathing. However, this is more likely to occur in premature babies (babies born before week 37 of pregnancy) and those born with a heart or lung condition.

Glossary

Respiratory tract
The respiratory tract is a general term used to describe all the parts of the body that are involved in helping a person breathe.

Bronchioles
The bronchioles are tiny airways found throughout the lungs.

Lungs
Lungs are a pair of organs in the chest that control breathing. They remove carbon dioxide from the blood and replace it with oxygen.

Inflammation
Inflammation is the body's response to infection, irritation or injury, which causes redness, swelling, pain and sometimes a feeling of heat in the affected area.