Croup usually develops as the result of a viral infection. The infection causes the larynx (voice box) to become swollen and the trachea (windpipe) to become blocked, and may affect the tubes in the lungs (bronchi). It is sometimes called laryngo-tracheo-bronchitis
The parainfluenza virus is the most common cause of croup. Four strains of the virus are responsible for most croup cases. These are:
Parainfluenza I is responsible for most cases of croup.
The virus can be transmitted through close contact with infected people, as well as contaminated objects and surfaces. As with many airborne viruses, the parainfluenza virus is often spread by breathing in droplets from infected coughs or sneezes.
A number of other viruses can also cause croup. These include:
Less common causes of croup include:
Croup is a childhood condition that affects the windpipe (trachea), the airways to the lungs (the bronchi) and the voice box (larynx).
Information about croup symptoms, including bark-like cough, difficulty breathing and rasping breath (stridor).
Information on the causes of croup, including flu viruses. The infection causes the larynx (voice box) to become swollen and the trachea (windpipe) to become blocked.
A GP can diagnose croup by studying your child's symptoms, particularly the sound of their cough. Croup typically causes a barking cough and rasping breathing (stridor).
The treatment of croup depends on how severe the symptoms are. Most cases do not need treating as the condition usually gets better on its own.
Complications that develop as a result of croup are rare.