What causes croup?

It's a virus.: Croup is caused by a virus. Most commonly, the parainfluenza virus. This virus infects the upper respiratory tract, more specifically, the larynx (voice box) and trachea (wind pipe). This is why children with croup end up with a hoarse voice and the telltale barking cough. Cases of croup peak in the fall and winter and are generally most common in children ages 3 months to 3 years.

Viral Infection: Croup describes an inflammation of the windpipe, that can be caused by many different viruses. Typical symptoms include a barky cough and noisy breathing (stridor). Treatment consists of cool mist or steam, and sometimes oral steroids or breathing treatments.

Can cause croup: Most cases of croup are caused by viruses, usually parainfluenza virus and sometimes adenovirus or respiratory syncytial virus (RSV).