RSV vs. Croup: Key Clinical Distinctions
RSV and croup are fundamentally different entities: RSV is a specific viral pathogen that causes respiratory infections, while croup is a clinical syndrome (laryngotracheobronchitis) characterized by barking cough, stridor, and upper airway obstruction that can be caused by multiple viruses, including RSV itself. 1, 2
What RSV Is
RSV is a specific virus (respiratory syncytial virus) from the Paramyxoviridae family that causes respiratory tract infections across all age groups. 3
- RSV exists in two antigenic subtypes (A and B) and is one of the most common pathogens causing lower respiratory tract disease in infants and young children. 3
- Clinical manifestations range from upper respiratory symptoms (cough, nasal discharge, sore throat) to severe bronchiolitis and pneumonia, particularly in infants under 1 year. 4, 5
- RSV infections peak during cold season (typically December through March in the Northern Hemisphere) and can cause serious disease in elderly adults and immunocompromised patients. 4, 3
- Cough is present in 93% of RSV cases, often accompanied by nasal congestion, shortness of breath, and sometimes fever. 4
What Croup Is
Croup is a clinical syndrome, not a specific virus, characterized by upper airway obstruction from swelling of the larynx, trachea, and bronchi. 6, 7
- The hallmark features are inspiratory stridor, barking cough, hoarseness, and respiratory distress. 6, 7
- Croup primarily affects children 6 months to 3 years of age and accounts for 7% of hospitalizations for fever/acute respiratory illness in children under 5 years. 6
- Parainfluenza viruses (types 1 and 2) are the primary cause of croup, not RSV, though RSV can occasionally cause croup as well. 1, 2
- Other viruses that can cause croup include rhinoviruses, coronaviruses, adenoviruses, influenza, and human metapneumovirus. 1
The Critical Overlap
RSV can cause croup, but it is not the typical pathogen. 1, 2
- When RSV does cause lower respiratory tract disease, it more commonly presents as bronchiolitis (inflammation of the small airways) rather than croup (upper airway obstruction). 2, 8
- Parainfluenza viruses and RSV are the two most common viral pathogens seen in children with respiratory infections, but they cause different clinical syndromes. 2
Treatment Differences
Croup treatment focuses on reducing airway inflammation and obstruction:
- Single dose of oral dexamethasone (0.15-0.6 mg/kg) is the mainstay of treatment for all severities of croup. 9, 6
- Nebulized epinephrine is added for moderate-to-severe croup with increased work of breathing. 9, 6
- Nebulized budesonide (2 mg) is an alternative for children who cannot tolerate oral dexamethasone. 9
RSV treatment is primarily supportive:
- Adequate hydration, supplemental oxygen if saturation falls below 90%, and symptomatic relief with acetaminophen or ibuprofen. 5
- Corticosteroids and bronchodilators are NOT routinely recommended for RSV bronchiolitis. 5
- Ribavirin is reserved for severely immunocompromised patients (such as hematopoietic stem cell transplant recipients) with RSV lower respiratory tract disease. 5, 8
Common Pitfall to Avoid
Do not confuse the pathogen (RSV) with the syndrome (croup). A child can have RSV infection without croup, and most cases of croup are NOT caused by RSV but by parainfluenza viruses. 1, 2 The treatment approach differs significantly based on the clinical presentation (upper airway obstruction vs. lower airway disease), not just the viral etiology.