Bronchiolitis

What bronchiolitis is

When a virus infects the bronchioles, their lining swells and produces mucus, and dead cells collect in the tiny airways. In a baby, whose airways are very small, this narrows them significantly. Air gets trapped, breathing becomes faster and harder, and oxygen levels can fall.

Almost all children have had RSV by age 2. Older children and adults usually get a cold, but babies can get bronchiolitis.

Symptoms

Bronchiolitis follows a typical course:

1. Days 1 to 2: runny nose, congestion, mild cough, sometimes a low fever.
2. Days 3 to 5 (worst period): worsening cough, fast breathing, wheezing or crackly sounds, working hard to breathe, poor feeding.
3. After day 5: gradual improvement over 1 to 2 weeks. The cough often lasts 3 to 4 weeks.

Signs of breathing difficulty to watch for:

• breathing faster than normal
• the skin pulling in between or under the ribs (retractions)
• flaring nostrils
• grunting at the end of each breath
• wheezing
• head bobbing with each breath
• pauses in breathing (apnea), especially in very young or premature babies, sometimes before other symptoms

Babies may also have difficulty feeding because they cannot breathe and suck at the same time, which can lead to dehydration.

Causes and risk factors

• RSV: the cause in most cases, especially severe ones.
• Other viruses: rhinovirus, human metapneumovirus, influenza, parainfluenza, adenovirus and coronaviruses.

Spread is through droplets and contaminated hands and surfaces.

Higher risk of severe illness:

• age under 3 months
• premature birth (before 37 weeks, and especially before 32 weeks)
• chronic lung disease of prematurity
• congenital heart disease
• weakened immune system
• neuromuscular conditions
• exposure to tobacco smoke
• not being breastfed
• older siblings in daycare, crowded living conditions

Bronchiolitis vs other conditions

Diagnosis

Doctors diagnose bronchiolitis by the history and examination: listening to the chest and measuring breathing rate and oxygen saturation with a finger or toe probe. Routine X-rays and blood tests are not recommended. A nasal swab for RSV or other viruses may be done in the hospital.

Treatment

Bronchiolitis is caused by a virus, so antibiotics do not help unless there is a separate bacterial infection. Guidelines from the American Academy of Pediatrics advise against routine use of:

• albuterol (salbutamol) inhalers
• steroids
• nebulized epinephrine
• chest physiotherapy
• antibiotics

Care at home

• Clear the nose: saline drops followed by gentle bulb suction before feeds and sleep.
• Small, frequent feeds: offer breast milk or formula more often than usual.
• Keep the air smoke-free.
• Fever and discomfort: acetaminophen (paracetamol) at the label dose for age and weight. Ibuprofen only for babies 6 months or older. No aspirin. No cough or cold medicines.
• Sleep: always on the back, in a clear crib, even when congested.
• Watch closely for the warning signs above, especially days 3 to 5.

Hospital care

About 2 to 3% of babies need admission, mainly for:

• oxygen if levels are low
• high-flow nasal cannula or other breathing support
• fluids through a nasogastric tube or IV if feeding is poor
• monitoring for apnea in young infants

Most hospital stays last 2 to 4 days.

Prevention

• Maternal RSV vaccine: given during pregnancy (at 32 to 36 weeks in season) to protect the baby through the first months.
• RSV monoclonal antibody (nirsevimab or a similar product): a single injection recommended for infants under 8 months entering their first RSV season if the mother did not receive the vaccine, and for some high-risk toddlers in their second season.
• Hand hygiene for everyone who handles the baby.
• Avoid contact with people who have colds, especially in the first months.
• No smoking around the baby or in the home or car.
• Breastfeeding reduces the risk of severe illness.

Outlook and long-term effects

Most babies recover fully. Some, particularly after severe RSV bronchiolitis, have recurrent wheezing in early childhood. It is unclear whether bronchiolitis causes asthma or whether children prone to asthma are more likely to have severe bronchiolitis.

Frequently asked questions

How long does bronchiolitis last?

Symptoms usually worsen over the first 3 to 5 days and then improve. Most babies are much better within 2 weeks, but a cough can last up to 4 weeks. Babies are usually contagious for 3 to 8 days, longer in young infants.

What are the warning signs of bronchiolitis?

Warning signs include breathing pauses, blue or gray lips, grunting, deep pulling in of the skin between the ribs, very fast breathing, poor feeding with few wet diapers, and unusual sleepiness or floppiness. These need urgent or emergency care.

Is bronchiolitis the same as bronchitis?

No. Bronchitis affects the larger airways (bronchi) and is more common in older children and adults, causing a cough. Bronchiolitis affects the tiny airways (bronchioles) of babies and young children and can cause significant breathing difficulty.

Do babies with bronchiolitis need antibiotics?

No, in most cases. Bronchiolitis is caused by viruses, so antibiotics do not help and can cause side effects. They are only used if a doctor finds a bacterial complication, such as an ear infection or pneumonia.

Can adults catch bronchiolitis from a baby?

Adults can catch the virus, usually RSV, and typically get a cold. Older adults and people with heart or lung disease can become seriously ill from RSV. Handwashing and avoiding close contact when sick help protect both babies and vulnerable adults.