Primary Cause of Croup

Viral Etiology of Croup

Parainfluenza viruses are the primary cause of croup, with types 1 and 2 most commonly associated with the croup syndrome 1
Parainfluenza viruses are responsible for up to 11% of all hospitalizations in children under 5 years of age 1
The clinical course of croup caused by influenza appears to be more severe than croup caused by the more common parainfluenza virus and is more likely to be complicated by bacterial tracheitis 2, 3

Other viruses that can cause croup include Respiratory syncytial virus (RSV), Rhinoviruses, Human coronaviruses, Adenoviruses, Influenza viruses, and Human metapneumovirus 1, 2, 3, 4

The histologic effects of viral infection vary from epithelial destruction to minimal changes, but all cause vasodilation and hypersecretion 5, 6

Bacterial tracheitis should be considered as a differential diagnosis when evaluating a child with suspected croup 7

Note: No management considerations are included as the provided citations are from 'Praxis Medical Insights' or include [ignore ref]

The American Academy of Pediatrics recommends annual influenza vaccination for all children ≥6 months of age, which can prevent influenza-associated croup, but does not protect against parainfluenza viruses, the primary cause of croup, in children with standard childhood immunizations that protect against Streptococcus pneumoniae (PCV13), Haemophilus influenzae type b, pertussis, and influenza 8
The Centers for Disease Control and Prevention recommends standard childhood immunizations, which protect against Streptococcus pneumoniae (PCV13), Haemophilus influenzae type b, pertussis, and influenza, but none of these are the primary cause of croup, and no vaccine exists for parainfluenza viruses in the standard childhood immunization schedule 8