83 Causes of Croup
Viruses
The main cause of croup is a viral infection. In fact, many cases are triggered by the same strain of viruses in influenza or the common cold, which is known as the parainfluenza virus. Many other viruses can also lead to this condition, including respiratory syncytial virus or RSV, adenovirus, influenza B and A viruses, rhinoviruses, or enteroviruses. These microorganisms can spread when you breathe in an air droplet from a sneezing or coughing person. Children and people with weakened immune systems tend to be at a higher risk because the viruses can penetrate their bodies more easily. [8]
