What Is Bronchiolitis?

Bronchiolitis is a common illness of infants and young children. It occurs during winter and early spring and affects the entire respiratory tract, including the bronchioles. The bronchioles are the smallest air passages of the lungs.

Bronchiolitis usually begins as a cold, often with symptoms of fever, runny nose or nasal stuffiness, and poor appetite or difficulty with sucking in infants. After two to four days, the virus spreads to the bronchioles, causing irritation and narrowing of these air passages. This results in a whistling sound (wheeze) when breathing out.

Bronchiolitis is usually mild, and the child gets better after three or four days. However, sometimes the infection is more serious and admission to a hospital is required.