Croup (Laryngotracheobronchitis) is a common childhood respiratory illness characterised by sudden onset of a seal-like barking cough, often accompanied by stridor, voice hoarseness, and respiratory distress. The symptoms are a result of inflammation and narrowing of the subglottic region of the larynx, as a result of viral infection (Typically parainfluenza virus types 1 or 3).
It most commonly affects children between 6 months and 6 years of age, with a peak incidence during the second year of life. Boys are slightly more commonly affected than girls, with a ratio of around 1.4 to 1.