Epidemiology

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• Primarily affects children < 2 years of age
• Peak incidence: 2–6 months of age
• Common during winter months
• Risk factors are the same as risk factors for severe RSV infection in children.

Etiology

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• Most common: respiratory syncytial virus (RSV), a paramyxovirus
• Less common
  • Parainfluenza virus

Pathophysiology

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Clinical features

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• Initially, URTI symptoms (e.g., copious rhinorrhea, low-grade fever, cough)
• Followed by LRTI symptoms
  • Crackles, wheezes, and/or rhonchi on auscultation
    • Wheezing in bronchiolitis is diffuse, polyphonic and classically “musical” in nature. Wheezing in asthma is more monophonic and improves with bronchodilator administration.
  • Severe illness: respiratory distress (usually occurs in children < 1 year of age)
    • Due to mucous obstruction of the bronchioles, which are very small in children < 2 years of age
    • Tachypnea or apnea
    • Prolonged expiration
    • Nasal flaring
    • Intercostal retractions
    • Cyanosis

Diagnostics

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Treatment

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