Bronchiolitis is a common lower respiratory tract infection that affects babies and young children under two years old.
Most cases are mild and clear up without the need for treatment within two to three weeks, although some children have severe symptoms and need hospital treatment.
Further symptoms then usually develop over the next few days, including:
Most cases of bronchiolitis aren't serious, but you should contact your GP if:
Your GP will usually be able to diagnose bronchiolitis based on your child's symptoms and by examining their breathing.
Dial 999 for an ambulance if:
Read more about diagnosing bronchiolitis.
Bronchiolitis is caused by a virus known as the respiratory syncytial virus (RSV), which is spread through tiny droplets of liquid from the coughs or sneezes of someone who's infected.
The infection causes the smallest airways in the lungs (the bronchioles) to become infected and inflamed. The inflammation reduces the amount of air entering the lungs, making it difficult to breathe.
Read more about the causes of bronchiolitis.
Around one in three children in the UK will develop bronchiolitis during their first year of life. It most commonly affects babies between three and six months of age. By the age of two, almost all infants will have been infected with RSV and up to half of these will have had bronchiolitis.
Bronchiolitis is most widespread during the winter (from November to March). It's possible to get bronchiolitis more than once during the same season.
There's no medication to kill the virus that causes bronchiolitis, but the infection usually clears up within two weeks without the need for treatment. Most children can be cared for at home in the same way that you'd treat a cold.
About 2-3% of babies who develop bronchiolitis during the first year of life will need to be admitted to hospital because they develop more serious symptoms, such as breathing difficulties. This is more common in premature babies (born before week 37 of pregnancy) and those born with a heart or lung condition.
It's very difficult to prevent bronchiolitis, but there are steps you can take to reduce your child's risk of catching it and help prevent the virus spreading. You should:
Some children who are at high risk of developing severe bronchiolitis may have monthly antibody injections, which help to limit the severity of the infection.
Read more about preventing bronchiolitis.