Children's Hospital Colorado

Bronchiolitis in Children

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What is bronchiolitis?

Bronchiolitis is a viral infection of the lungs that affects infants and young children. Bronchiolitis begins as a cold with a runny nose and then moves down into the lungs and the small airways of the lung, known as the bronchioles. As these airways become inflamed, they swell and fill with mucus, making breathing difficult.

Although it's usually a mild illness, some children develop more severe bronchiolitis that requires admission to the hospital. Bronchiolitis is the most common reason for babies to be admitted to the hospital with more than 100,000 hospital admissions each year. It is most common in the winter and spring.

Some conditions increase the risk that a child will develop severe bronchiolitis. They include prematurity (born more than 2 weeks early), prior chronic heart or lung disease, a weakened immune system due to illness or medications, or muscle weakness.

What causes bronchiolitis?

Bronchiolitis is usually caused by a viral infection, most commonly respiratory syncytial virus (RSV). Other viruses associated with bronchiolitis include rhinovirus, influenza (flu) and human metapneumovirus, the same virus that causes the common cold in older children and adults.

The viruses that cause bronchiolitis are contagious. The germs can spread in tiny drops of fluid from an infected person's nose and mouth, which may get into the air with sneezes, coughs or laughs, and can end up on things the person has touched, such as tissues or toys. The incubation period (the time between infection and the beginning of symptoms) ranges from several days to a week, depending on the type of virus causing the bronchiolitis.

The best way to prevent the spread of viruses that can cause bronchiolitis is frequent hand washing. It may help to keep infants away from others who have colds or coughs. Flu shots are recommended for infants 6 months of age or older and for all family members and caregivers of infants.

For infants at high risk for severe bronchiolitis (who were premature or have chronic lung or heart disease), there is an injection called Synagis (palivizumab) that can decrease the baby’s chances of being admitted to the hospital with an RSV infection. The injection is given monthly during the winter months, and should be discussed with your medical provider if you think your infant may qualify.

Who gets bronchiolitis?

Bronchiolitis is common and typically occurs during the first 2 years of life, most commonly between 3 to 6 months of age. It most often affects infants and young children because their airways are smaller and can become blocked with mucus more easily than those of older kids or adults.

Infants with a history of prematurity, congenital heart or lung disease, a weakened immune system, or muscle weakness are at higher risk of severe bronchiolitis. Babies who are exposed to cigarette smoke are more likely to develop more severe bronchiolitis and be hospitalized compared with those from smoke-free homes. It is important for all children to avoid exposure to cigarette smoke.

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Get to know our pediatric experts.

Anna Hamilton, CPNP-AC

Anna Hamilton, CPNP-AC

Certified Pediatric Nurse Practitioner

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Grace Houser, MD

Grace Houser, MD

Pulmonology - Pediatric, Pediatrics

Mary Conyers, CPNP-PC

Mary Conyers, CPNP-PC

Certified Pediatric Nurse Practitioner

Robin Deterding, MD

Robin Deterding, MD

Pulmonology - Pediatric