Bronchiolitis is an inflammation of the bronchioles (smaller airways that branch off the main airway) usually caused by a viral infection.
Review Date 1/1/2020
Updated by: Neil K. Kaneshiro, MD, MHA, Clinical Professor of Pediatrics, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.