Background: Historically croup was subdivided into classic "viral" croup with associated viral upper respiratory tract infections, and recurrent or spasmodic croup where asthma and allergies were thought more important.
Methods: All children admitted to the University Hospital of Wales with croup in 2003 were eligible. Baseline demographics including croup score were recorded and per-nasal swabs taken for virus detection by RT-PCR. Recurrent croup was defined as at least one other admission for croup in the preceding or following 3 years.
Results: Sixty (29.4%) children entered the study, and a viral pathogen was detected in 41 (68%). There was no significant difference in the rate of virus detection between those with single episode croup and recurrent croup.
Conclusions: The aetiologies of viral and recurrent croup appear similar.