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Bronchiolitis and RSV

What is bronchiolitis?

Bronchiolitis is a viral chest infection that affects babies and children under two years old more severely than older children. It's most commonly caused by the respiratory syncytial virus (RSV). On this page we explain how children can be affected by bronchiolitis, who is at higher risk and how serious bronchiolitis can be.

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What is bronchiolitis?

Bronchiolitis is an infection of the smaller airways in the lungs (called the bronchioles). It’s more common in babies and very small children up to two years old  and is commonly caused by the respiratory syncytial virus (RSV). Read more about the causes of bronchiolitis.

Different conditions of similar names

Bronchiolitis should NOT be confused with a very rare condition called bronchiolitis obliterans (even though they share a similar name). 

Bronchiolitis vs bronchitis?

Although the names sound similar, bronchitis is another different condition. Bronchitis is an infection affecting the larger airways (called the bronchi). Long-term (chronic) bronchitis is a form of chronic obstructive pulmonary disease (COPD).

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How are babies and toddlers affected by bronchiolitis?

Bronchiolitis usually starts like the common cold. It can make your baby or toddler cough and become breathless. This makes it hard for them to breathe and feed. Read more about the different symptoms of bronchiolitis.

Bronchiolitis usually starts with a runny or blocked nose, and over 2-3 days the infection may pass down to the  smaller airways (bronchioles) in your child’s lungs causing them to become inflamed and clogged up with mucus.

In most cases their breathing and feeding will get better within five days. Their cough might last longer.

Is my child at risk?

Bronchiolitis is more common in babies and very small children up to two years old.  It’s most common up to the age of six months.

Some babies and children are at greater risk of developing severe bronchiolitis:

  • premature babies, or those who were born with a lower-than-average birth weight
  • babies with existing heart or lung conditions 
  • babies with poorly developed immune systems 
  • children with Down’s syndrome. 

Exposure to tobacco smoke makes it more likely for a baby or toddler to develop more severe bronchiolitis.  Read more about how passive smoking and vaping affects your child’s lungs.

Your baby or toddler is most likely to develop bronchiolitis in the UK between October and March when respiratory viral infections are more common.

How serious can bronchiolitis be?

Most children only develop mild symptoms which clear up after a few days, and clear up fully usually after less than a month. Almost all make a full recovery with no long-term effects.

Some children will experience more severe bronchiolitis symptoms. After severe bronchiolitis, it’s not uncommon for children to have a cough for weeks or months following the infection. Some may experience intermittent noisy breathing (called wheezing). It is very rare for babies and children without underlying health problems to die from bronchiolitis. 

If your child has severe symptoms of bronchiolitis, get in touch with a health care professional. Out of hours, call NHS 111 (in England and Scotland), NHS 111 Wales or 0845 46 47 (in Wales) or your local out-of-hours service (in Northern Ireland).

Call 999 for urgent help if:

  • your child is struggling to breathe. They may grunt or draw the muscles under their chest in when they breathe. This makes them look like they are breathing with their tummy.
  • your child’s breathing stops for 20 seconds or longer on one occasion, or there are regular shorter pauses in their breathing.
  • the colour of your baby's skin inside the lips or under the tongue turns blue.

Read next: What are the symptoms of bronchiolitis?

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Last medically reviewed: November 2021. Due for review: November 2024

This information uses the best available medical evidence and was produced with the support of people living with lung conditions. Find out how we produce our information. If you’d like to see our references get in touch.