Croup is a viral infection that causes erythema and edema of the tracheal walls and narrowing of the subglottic region. It is often characterized by an acute, rapidly progressing respiratory disease.
It is a medical emergency in children and requiring immediate treatment.
Most common causes are parainfluenza virus 1&2 and respiratory syncytial virus.
Occurrence of symptoms is usually at night and with abrupt onset and improve during daytime.