What causes croup?The parainfluenza virus is a family of viruses that accounts for 75% of cases of croup. Croup symptoms often develop a few days after the start of what appears to be an upper respiratory infection (URI), such as a cold. Most cases are caused by human parainfluenza viruses types I and II. However, other viruses, such as influenza viruses types A and B, respiratory
syncytial virus (RSV), and measles, can also cause croup. As children grow older and structures in the throat and breathing tubes mature, they are less susceptible to croup.
Viral croup is the most common. Other possible causes include bacteria, allergies, and inhaled irritants. Acid reflux from the stomach can trigger croup. Croup is usually (75 percent of the time) caused by parainfluenza viruses, but RSV, measles, adenovirus, andinfluenzacan all cause croup. Before the era of immunizations and antibiotics, croup was a dreaded and deadly disease, usually caused by the diphtheria bacteria. Today, most cases of croup are mild. Nevertheless, it can still be dangerous. Croup tends to appear in children between 3 months and 5 years old, but it can happen at any age. Some children are prone to croup and may get it several times.
In the Northern hemisphere, it is most common between October and March, but can occur at any time of the year. In severe cases of croup, there may also be a bacterial super-infection of the upper airway. This condition is called bacterial tracheitis and requires hospitalization and intravenous antibiotics. If the epiglottis becomes infected, the entire windpipe can swell shut, a potentially fatal condition called epiglottitis.