Bronchiolitis: Causes, Symptoms, and Treatment
Also known as: RSV bronchiolitis
Overview
Bronchiolitis is an acute viral infection of the lower airways that mainly affects infants under 2 years old. In the United States, it’s a major public health concern: RSV-related bronchiolitis leads to an estimated 58,000 to 80,000 hospitalizations of children under 5 each year, according to the CDC, mostly during fall and winter. The condition involves inflammation and blockage of the small airways (bronchioles), causing breathing difficulty that ranges from mild to severe.
Causes and risk factors
Bronchiolitis is caused most often by respiratory syncytial virus (RSV), which is responsible for the majority of cases, though other viruses can also be responsible: rhinovirus, human metapneumovirus, adenovirus, or influenza virus. It spreads through direct contact with an infected person’s nasal secretions or contaminated hands. Main risk factors include:
- Age under 6 weeks
- Prematurity or congenital heart disease
- Bronchopulmonary dysplasia
- Secondhand smoke exposure
- Attending daycare
- Young siblings at home
Symptoms
Bronchiolitis typically progresses in two phases. It starts with cold-like symptoms (runny nose, mild fever) for 1 to 3 days, then characteristic respiratory signs appear:
- Persistent, repetitive dry cough
- Breathing difficulty with rapid breathing (tachypnea)
- Wheezing on exhale
- Crackling sounds heard through a stethoscope
- Feeding difficulties (reduced intake)
- In severe cases: flaring nostrils, chest retractions, bluish skin (cyanosis)
Diagnosis
Bronchiolitis diagnosis is mostly clinical: the doctor relies on a physical exam (lung sounds, assessing breathing difficulty) and the child’s history. In routine cases, no additional testing is needed. For severe cases or hospitalization, pulse oximetry (oxygen saturation), a chest X-ray, and a nasal viral swab may be performed.
Treatments
Bronchiolitis care is mainly supportive, since there’s no specific approved antiviral treatment. Current pediatric guidance favors:
- Regular nasal saline rinses and suctioning, before feeds and bedtime, an essential step repeated several times a day
- Smaller, more frequent feeds to reduce breathing effort during feeding
- Adequate hydration and weight monitoring
- Elevating the head slightly to ease breathing
- Fever reducers (acetaminophen) for fever or discomfort
- Hospitalization for severe breathing distress, dehydration, or apnea episodes
- Oxygen therapy in the hospital if oxygen saturation drops below 90%
- Chest physiotherapy is no longer routinely recommended for mild to moderate cases
Prevention
Several measures help limit RSV transmission and protect vulnerable infants:
- Regular hand washing with soap and water or hand sanitizer
- Avoiding crowded indoor spaces and group childcare during peak season for very young infants
- Daily ventilation of the home
- Avoiding secondhand smoke around infants
- Breastfeeding, recommended for its protective immune properties
- Nirsevimab (Beyfortus): a monoclonal antibody approved by the FDA and recommended by the CDC and AAP for infants under 8 months entering their first RSV season, offering strong protection against severe disease
When should you see a doctor?
See a doctor promptly if your infant has rapid breathing, visible chest retractions, bluish lips or nails, poor feeding (less than half their usual intake), persistent fever, or episodes of apnea. Call 911 for severe breathing distress or if your baby seems to be in shock.
Sources
- CDC: RSV in Infants and Young Children, an estimated 58,000 to 80,000 RSV-associated hospitalizations among children younger than 5 each year
- American Academy of Pediatrics (AAP), official U.S. pediatric clinical guidance
- MedlinePlus: Bronchiolitis, U.S. National Library of Medicine; affected age group, symptoms, and emergency warning signs
- StatPearls: Bronchiolitis (NCBI Bookshelf), RSV as the majority cause, clinical diagnosis, supportive care, and the goal of keeping oxygen saturation just above 90%
- ACIP: Use of Nirsevimab for the Prevention of RSV Disease (MMWR, 2023), CDC/ACIP recommendation of nirsevimab for infants under 8 months in their first RSV season