Causative Organism of Croup
Parainfluenza viruses, particularly types 1 and 2, are the primary cause of croup. 1
Primary Viral Etiology
- Parainfluenza viruses are responsible for the majority of croup cases, with types 1 through 3 being the most common causative agents 1, 2, 3
- These viruses account for up to 11% of all hospitalizations in children under 5 years of age 1
- Parainfluenza virus is consistently identified as the predominant pathogen across multiple studies 4, 5
Secondary Viral Causes
While parainfluenza is the leading cause, several other viruses can also cause croup:
- Respiratory syncytial virus (RSV) is the second most common viral cause 1, 5
- Influenza viruses can cause croup, though the clinical course tends to be more severe than parainfluenza-associated croup and carries higher risk of bacterial tracheitis complications 1
- Other less common viral causes include rhinoviruses, human coronaviruses, adenoviruses, and human metapneumovirus 1
Clinical Context
- Croup is a viral illness affecting children primarily between 6 months and 6 years of age 2, 4
- The viral infection causes vasodilation and hypersecretion in the larynx and trachea, leading to the characteristic barking cough and stridor 1
- While croup is viral in origin, bacterial tracheitis should be considered in the differential diagnosis, particularly in severe or atypical presentations 1