J20-J22: Other acute lower respiratory infections

J21: Acute bronchiolitis

Acute bronchiolitis is a group of conditions affecting the bronchioles, the small airways in the lungs. It typically occurs in children under two years of age, and is often caused by a viral infection, most commonly the respiratory syncytial virus (RSV). Other viruses such as the influenza and parainfluenza viruses can also cause these conditions. Acute bronchiolitis often starts with symptoms similar to those of a common cold, including runny nose, mild cough, and mild fever. As it progresses, it may cause wheezing, fast and shallow breathing, shortness of breath, and a bluish skin color due to lack of oxygen. The conditions can range from mild to severe, occasionally requiring hospitalization. These illnesses spread through droplets from a cough or sneeze, or by touching contaminated surfaces, and tend to be more common in the winter months.