AEMCA Practice Exam 2026 – All-in-One Comprehensive Study Guide for Exam Success!

Croup is primarily caused by viral infections, with the parainfluenza virus being one of the most common culprits. This virus leads to inflammation and swelling of the upper airways, which causes the characteristic symptoms of croup, such as a barking cough, stridor, and respiratory distress.

While other pathogens are associated with respiratory illnesses, they are not typical causes of croup. Streptococcus pneumoniae is mainly known for causing bacterial pneumonia and other infections, while E. coli is primarily associated with gastrointestinal and urinary tract infections. Herpes simplex virus is known for causing cold sores and oral herpes, rather than respiratory issues like croup.

Thus, identifying the parainfluenza virus as the cause of croup aligns with established medical knowledge about the disease's viral etiology.