Croup or Acute Laryngotracheobronchitis (ALTB) is a viral infection of the throat (upper airway). The virus causes swelling of the voice box (larynx) and windpipe (trachea). The swelling narrows the airway and makes breathing hard.

Croup can get worse quickly. If your child is having problems breathing, he or she should get medical help as soon as possible. If your child has croup, you should consider sleeping overnight in the same room to observe him or her closely. If you are not able to ease your child's shortness of breath and croupy cough, call your child's doctor or seek medical attention as soon as possible.