What is the primary cause of bronchiolitis in children?

The primary cause of bronchiolitis in children is Respiratory Syncytial Virus (RSV). This viral infection predominantly affects infants and young children, causing inflammation and congestion in the small airways of the lungs, known as bronchioles. RSV is particularly known for its seasonal outbreaks and is the leading cause of lower respiratory tract infections in children under two years of age.

Understanding the significance of RSV is crucial for recognizing the clinical presentation of bronchiolitis, which typically includes wheezing, coughing, and respiratory distress. Other viruses, such as the influenza virus and parainfluenza virus, may cause respiratory illnesses, but they are not the primary pathogens associated with bronchiolitis. Rhinovirus, while also capable of causing respiratory symptoms, is less frequently implicated in the specific diagnosis of bronchiolitis compared to RSV. Thus, RSV's well-established role in the pathogenesis of bronchiolitis underscores its recognition as the most common cause among the options provided.