Bronchiolitis means inflammation of the bronchioles - tiny airways in the lung. Bronchiolitis is a type of chest infection. It is usually caused by a viral infection called respiratory syncytial virus (RSV). Other viruses are sometimes the cause. RSV is a common cause of colds. In some babies RSV can also infect lower down the airways to cause bronchiolitis. RSV is spread in tiny water droplets coughed and sneezed into the air. Infected bronchioles become swollen and full of mucus.
This is a companion discussion topic for the original article at https://patient.info/chest-lungs/bronchiolitis-leaflet