Respiratory syncytial virus (RSV)
Respiratory syncytial virus is the leading cause of bronchiolitis and infant hospitalization for lower respiratory tract infection, peaking in fall and winter in children under two years. Diagnosis is clinical; management is supportive, and prevention now centers on universal infant immunoprophylaxis with nirsevimab or maternal RSV vaccination.
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What this article covers
- Overview
RSV is the dominant cause of bronchiolitis, an acute inflammatory illness of the small lower airways that primarily affects infants and children under 2 years of age; RSV causes roughly half of…
- Epidemiology
The most common cause of bronchiolitis in children younger than 2, causing winter and spring epidemics.
- Risk factors
Age under 6 months, the group at highest risk of severe disease and apnea.
- Pathophysiology
RSV, a paramyxovirus, infects respiratory epithelial cells via its surface fusion (F) glycoprotein, causing infected cells to fuse into multinucleated syncytia, the pathologic hallmark behind the virus's name.
- Clinical features
The illness begins as a mild upper respiratory infection (rhinorrhea, mild fever, cough) for 1 to 3 days before lower tract symptoms emerge.
- Differential diagnosis
Viral pneumonia (non-RSV or RSV pneumonia): overlapping tachypnea and hypoxia, but focal consolidation and a less prominent wheeze favor pneumonia over bronchiolitis.
- Diagnosis
Bronchiolitis is a clinical diagnosis (age under 2, viral prodrome, wheezing/crackles with tachypnea in season, as above); routine cases require no laboratory or radiologic workup.
- Management
Start with supportive care, the backbone of treatment for essentially all bronchiolitis: supplemental oxygen to an age-appropriate saturation target, nasal bulb or deep suctioning before feeds and…
- Complications
Respiratory failure, the most feared complication, from progressive airway obstruction and fatigue; the reason for close monitoring of respiratory rate and work of breathing.
- Prognosis
Most infants recover fully with supportive care alone, typically over 1 to 2 weeks, with cough sometimes persisting longer.
- Prevention
Universal infant immunoprophylaxis with nirsevimab, a long-acting RSV monoclonal antibody, is recommended for all infants entering their first RSV season: a single IM dose of 50 mg for infants under…
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