Bronchiolitis is a lower respiratory tract infection (RTI) in which the bronchioles become inflamed because of a viral infection. Most often, the respiratory syncytial virus (RSV) is responsible. The infection occurs mainly in children below the age of two and is characterized by initial upper RTI symptoms (low-grade fever, stuffy nose) followed by a cough and possibly signs of respiratory distress (i.e., tachypnea, wheezing, nasal flaring, intercostal retractions, cyanosis) that may require hospitalization. Ill children should be closely monitored and receive oxygen and proper hydration for supportive therapy.
- Primarily affects children < 2 years
- Peak incidence: 2–6 months of age
- Common during winter months
Epidemiological data refers to the US, unless otherwise specified.
- Initially presents with upper respiratory tract symptoms (e.g., rhinorrhea), low-grade fever, and cough
- Respiratory distress (usually occurs in infants)
- Poor feeding in breastfed infants
- Auscultatory findings: wheezing, crackles
An upper RTI followed by symptoms of respiratory distress and wheezing in a child < 2 years of age should prompt evaluation for bronchiolitis.
- Bronchiolitis is a clinical diagnosis.
- Additional testing (not routinely done)
The differential diagnoses listed here are not exhaustive.
Pharmacologic treatment 
- Bronchodilators, epinephrine, and corticosteroids have historically been part of the treatment for bronchiolitis, but recent guidelines recommend using such therapies mainly in severe cases.
- Ribavirin: currently not recommended for routine treatment of bronchiolitis; may be considered in immunocompromised patients
- Adequate hydration
- Relief of nasal congestion/obstruction
- Indications for hospitalization
We list the most important complications. The selection is not exhaustive.
- Short-acting monoclonal antibody against RSV F protein that provides passive immunization to RSV infection
- Indications: infants at risk for severe bronchiolitis (e.g., prematurity, heart or lung disease, immunocompromised states)
- Monthly IM administration during RSV season for the first year of life