Bronchiolitis is a lower respiratory tract infection that occurs in children younger than two years old. The virus causes inflammation of the small airways (bronchioles).
The inflammation partially or completely blocks the airways, which causes wheezing (a whistling sound heard as the child breathes out). This means that less oxygen enters the lungs, potentially causing a decrease in the blood level of oxygen.
Bronchiolitis is a common cause of illness and is the leading cause of hospitalization in infants and young children. Treatment includes measures to ensure that the child consumes adequate fluids and is able to breathe without significant difficulty. Most children begin to improve two to five days after first developing breathing difficulties, but wheezing can last for a week or longer. Bronchiolitis can cause serious illness in some children. Infants who are very young, born early, have lung or heart disease, or have difficulty fighting infections or handling oral secretions are more likely to have severe disease with bronchiolitis.