Children's Hospital Colorado

Bronchiolitis in Children

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What is bronchiolitis?

Bronchiolitis is a viral infection in the lungs. In babies and young children, bronchiolitis typically starts with upper respiratory symptoms that look like a common cold (such as a stuffy, runny nose). Bronchiolitis in children usually resolves on its own, but some children develop more severe cases that require a hospital stay.

If it progresses, bronchiolitis can move down into the small airways of the lungs called the bronchioles. When the infection reaches these airways, they swell and fill with mucus, making it difficult to breathe. Trouble breathing can lead to bronchiolitis wheezing — a high-pitched whistling sound as your child breathes.

What causes bronchiolitis?

Bronchiolitis is caused by respiratory viruses. Most cases happen in babies who have respiratory syncytial virus (RSV). It may also develop after having a common cold or influenza (flu).

The viruses that cause bronchiolitis are found in small drops of fluid in an infected person's nose and mouth. These droplets spread through the air through sneezes, coughs or laughing. The germs can also end up on things the infected person has touched, such as doorknobs, toys and tissues.

You and your child can help prevent bronchiolitis by washing hands frequently and avoiding those who have a cold or flu. You should also keep infants away from others who have colds or coughs and avoid crowded places where germs spread easily. Infants 6 months of age or older and all family members and caregivers of infants should get an annual flu and COVID vaccine.

Who gets bronchiolitis and how common is it?

Bronchiolitis typically affects children under age 2. Most cases occur in babies 3 to 6 months old because babies’ small airways are more easily blocked with mucus than older kids or adults. Bronchiolitis is the most common reason babies are admitted to the hospital — about 100,000 infants require advanced care each year. Bronchiolitis illness affects children most frequently in the winter and spring.

Risk factors that increase a baby’s chance of getting bronchiolitis and having more severe symptoms include:

  • Prematurity (born at least 2 weeks early)
  • Congenital heart or lung disease
  • Weakened immune system
  • Muscle weakness
  • Exposure to cigarette smoke

If your baby is at high risk for severe bronchiolitis, ask your child’s pediatrician if they should receive the Synagis (palivizumab) vaccine. This injection can decrease your baby’s chances of being admitted to the hospital with an RSV or bronchiolitis infection.

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Get to know our pediatric experts.

Lisa Connell, CPNP-AC

Lisa Connell, CPNP-AC

Certified Pediatric Nurse Practitioner, Certified Pediatric Nurse Practitioner

Patient ratings and reviews are not available Why?

Alexandra Craig, CPNP-AC

Alexandra Craig, CPNP-AC

Certified Pediatric Nurse Practitioner

Patient ratings and reviews are not available Why?

Bridget Raleigh, FNP-BC

Bridget Raleigh, FNP-BC

Certified Family Nurse Practitioner