Risk factors are the same as risk factors for severe RSV infection in children.
Etiology
Most common: respiratory syncytial virus (RSV), a paramyxovirus
Less common
Parainfluenza virus
Pathophysiology
Clinical features
Prodrome: Viral URI symptoms (rhinorrhea, nasal congestion) for 2-3 days.
Progression: Low-grade fever, cough, tachypnea, increased work of breathing (grunting, nasal flaring, intercostal/subcostal retractions).
Auscultation: Diffuse polyphonic wheezing, fine crackles/rales, prolonged expiratory phase.
Wheezing in bronchiolitis is diffuse, polyphonic and classically “musical” in nature. Wheezing in asthma is more monophonic and improves with bronchodilator administration.
Red Flags: Hypoxia (SpO2 < 90%), apnea (classic presentation in infants < 2 months), poor feeding leading to dehydration, lethargy. c
Apnea in RSV bronchiolitis is often a central apnea. The exact mechanism is thought to be a combination of the immaturity of the neonatal brainstem respiratory center and the direct effects of the virus.