Acute bronchiolitis is an infection of the broncheoles, which are part of the lower airways of the respiratory(breathing) system. It usually affects children under 12mths. Serious cases may need to go to hospital. It is caused by various viruses, incl the flu virus and others, eg rhinovirus. The viruses infect the airways and cause swelling and excessive mucous production and also irritation.
Attribution: Avallain