• Clinical science



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.



Clinical features

  • Initially presents with upper respiratory tract symptoms (e.g., rhinorrhea), 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)


Differential diagnoses

The differential diagnoses listed here are not exhaustive.


  • Supportive treatment (adequate hydration, relief of nasal congestion/obstruction, monitoring)
  • Indications for hospitalization
  • Bronchodilators, epinephrine, and corticosteroids have historically been part of the treatment for bronchiolitis, but recent guidelines no longer recommend them.
  • Ribavirin (antiviral synthetic nucleoside analog): currently not recommended for routine treatment of bronchiolitis; may be considered in immunocompromised patients



We list the most important complications. The selection is not exhaustive.


  • With timely diagnosis and adequate treatment, the prognosis is good
  • Bronchiolitis in infancy is associated with an increased risk of developing asthma.



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  • 2. Maraqa NF. Bronchiolitis. In: Steele RW. Bronchiolitis. New York, NY: WebMD. http://emedicine.medscape.com/article/961963. Updated January 30, 2017. Accessed March 27, 2017.
  • 3. Barr FE, Graham BS. Bronchiolitis in Infants and Children: Clinical Features and Diagnosis. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. http://www.uptodate.com/contents/bronchiolitis-in-infants-and-children-clinical-features-and-diagnosis. Last updated November 3, 2016. Accessed March 27, 2017.
  • 4. Ralston SL, Lieberthal AS, Meissner HC, et al. Clinical practice guideline: the diagnosis, management, and prevention of bronchiolitis. Pediatrics. 2014; 134(5): pp. e1474–1502. doi: 10.1542/peds.2014-2742.
  • 5. Piedimonte G, Perez MK. Respiratory syncytial virus infection and bronchiolitis. Pediatr Rev. 2014; 35(12): pp. 519–530. doi: 10.1542/pir.35-12-519.
last updated 10/30/2020
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