Can Respiratory Syncytial Virus (RSV) cause croup?

Can RSV Cause Croup?

Yes, Respiratory Syncytial Virus (RSV) can cause croup, although it is less commonly associated with croup than parainfluenza viruses. 1

Viral Etiology of Croup

Croup (laryngotracheobronchitis) is primarily caused by viral infections, with the following pathogens being most commonly implicated:

• Parainfluenza viruses: Types 1 and 2 are most commonly associated with croup syndrome 1
• Respiratory Syncytial Virus (RSV): Second most common cause after parainfluenza viruses 2
• Human metapneumovirus: Can also cause croup in children 1, 3
• Other viruses: Including influenza and coronaviruses

Clinical Presentation of RSV-Associated Croup

When RSV causes croup, it presents with the classic symptoms:

• Barking cough
• Inspiratory stridor
• Hoarseness
• Respiratory distress

RSV more commonly causes:

• Bronchiolitis (especially in infants)
• Pneumonia
• Upper respiratory tract infections

Epidemiology and Risk Factors

RSV infections typically occur in seasonal outbreaks from December through March 1. While RSV can affect people of all ages, certain populations are at higher risk for severe disease:

• Infants and young children under 5 years
• Older adults (especially those >75 years) 1
• Immunocompromised individuals 1, 4
• Patients with chronic conditions such as:
  • Chronic lung disease
  • Heart disease
  • Diabetes 1
  • Chronic kidney disease 1

Diagnostic Considerations

When evaluating a patient with suspected croup:

1. Clinical diagnosis: Typically based on characteristic barking cough and stridor
2. Viral testing:
   • Respiratory secretions or nasopharyngeal swabs placed in viral transport medium 1
   • Nucleic acid amplification tests (NAATs) are now common in commercial respiratory panels 1
   • Rapid antigen detection tests are available for RSV 1

Clinical Pearls and Pitfalls

• Differential diagnosis: Always consider other causes of stridor beyond viral croup, especially when presentation is atypical or response to standard treatment is poor 5
• Prolonged course: While croup is typically self-limited, RSV and other pathogens can cause a protracted course in some cases 6
• Bacterial superinfection: Consider bacterial tracheitis as a complication, especially in cases not responding to standard therapy 6
• Age considerations: RSV-associated croup is more common in children, but RSV can cause respiratory illness in all age groups 1

Treatment Approach

Treatment of RSV-associated croup follows the same principles as croup from other viral causes:

1. Corticosteroids: Oral dexamethasone (0.15-0.6 mg/kg) for moderate to severe croup 2
2. Nebulized epinephrine: For severe cases with respiratory distress 2
3. Supportive care: Including hydration and monitoring of respiratory status
4. Observation: After treatment with epinephrine, patients require observation for potential rebound symptoms 2

In immunocompromised patients with severe RSV infection, ribavirin may be considered, though clinical trials specifically for RSV-associated croup are limited 4.