Croup is a type of respiratory infection that is usually caused by a virus. The infection leads to swelling inside the wind pipe, which interferes with normal breathing and produces the classic symptoms of “barking” cough, stridor, and a hoarse voice. Fever and runny nose may also be present. These symptoms may be mild, moderate, or severe. Often it starts or is worse at night. It normally lasts one to two days.
Croup can be caused by a number of viruses including parainfluenza and influenza virus. Rarely it is due to a bacterial infection. Croup is typically diagnosed based on signs and symptoms after potentially more severe causes such as epiglottitis or an airway foreign body have been ruled out. Further investigations—such as blood tests, X-rays, and cultures—are usually not needed.
Many cases of croup are preventable by immunization for influenza and diphtheria. Croup is usually treated with a single dose of steroids by mouth. In more severe cases inhaled epinephrine may also be used. Hospitalization is required in one to five percent of cases.