Croup epidemiology and demographics

Overview
Croup is most often caused by parainfluenza virus, primarily types 1 and 3, but other viral and possibly bacterial infections can also cause it. It is most common in the fall and winter but can occur year-round, with a slight predilection for males.

Epidemiology
Croup affects about 15% of children, and usually presents between the ages of 6 months and 5–6 years. It accounts for about 5% of hospital admissions in this population. In rare cases, it may occur in children as young as 3 months and as old as 15 years. Males are affected 50% more frequently than are females, and there is an increased prevalence in autumn (fall).