Britannica Sources used in this answer

How does respiratory syncytial virus cause bronchiolitis in young children?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Medical illustration of the human chest showing the lungs, diaphragm, ribs, trachea, bronchus, and bronchioles, with one lung cut away to reveal internal structures. — respiratory disease The bronchioles of the lungs are the site where oxygen is exchanged for carbon dioxide during the process of respiration. Inflammation, infection, or obstruction of the bronchioles is often associated with acute or chronic respiratory disease, including bronchiectasis, pneumonia, and lung abscesses.

Respiratory syncytial virus (RSV) causes bronchiolitis in young children primarily by infecting the respiratory system. The virus utilizes a specific surface component known as the F protein (fusion protein) to attach to and infect host cells.12

Once the virus invades the respiratory tract, it triggers inflammation that can lead to severe lower respiratory disease, particularly in infants under six months of age. This infection results in the inflammation of the bronchioles—the smallest airways in the lungs—which causes symptoms such as wheezing, rapid or labored breathing, and significant breathing difficulties. Because RSV effectively evades the immune system, it remains a major cause of these severe respiratory conditions in young children, often occurring as an annual epidemic during winter months.1