Objectives Bronchiolitis . Define bronchiolitisDescribe etiology and prevalence Define clinical manifestations Describe pathophysiologyDescribe diagnosis and treatmentIdentify strategy for prevention . Definition Bronchiolitis. Bronchiolitis is an acute inflammation of the bronchioles (smaller airways that branch off the main airway) and is usually caused by a viral infection that occurs primarily in young infants, most often in those aged 2-24 months. .