What is the most common viral cause of acute bronchiolitis?

The most common viral cause of acute bronchiolitis is Respiratory Syncytial Virus (RSV). This virus is particularly prevalent in infants and young children, and it plays a significant role in the pathogenesis of bronchiolitis, which is characterized by inflammation of the small airways in the lungs. RSV leads to increased mucus production and airway obstruction, resulting in the classic symptoms of wheezing, difficulty breathing, and coughing accompanying bronchiolitis.

RSV is known for its seasonality, often peaking during the fall and winter months, and it can cause severe respiratory illness in infants, especially those who are premature or have underlying health conditions. Its ability to infect and cause inflammation in the bronchioles makes it the primary viral agent associated with acute bronchiolitis, positioning it as the leading cause compared to other viruses.

Other viruses listed, such as adenovirus, influenza virus, and parainfluenza virus, can also cause respiratory infections, but they do not have the same association with bronchiolitis as RSV does. While these viruses can cause similar symptoms or even contribute to respiratory illnesses, their incidence and role in specific cases of acute bronchiolitis are much less frequent than that of RSV.