Definition of Bronchiolitis:

Bronchiolitis is swelling and mucus buildup in the smallest air passages in the lungs (bronchioles), usually due to a viral infection.

Causes, incidence, and risk factors:

Bronchiolitis usually affects children under the age of 2, with a peak age of 3 - 6 months. It is a common, and sometimes severe illness. Respiratory syncytial virus (RSV) is the most common cause. More than half of all infants are exposed to this virus by their first birthday.

Other viruses that can cause bronchiolitis include:

• Adenovirus
• Influenza
• Parainfluenza

You can catch the virus if you come into direct contact with nasal fluids or airborne droplets from someone who has the illness. This may happen if the person sneezes or coughs near you.

Bronchiolitis is seasonal and appears more often in the fall and winter months. It is a very common reason for infants to be hospitalized during winter and early spring.

Risk factors for bronchiolitis include:

• Being around cigarette smoke
• Age younger than 6 months old
• Living in crowded conditions
• Not being breastfed
• Prematurity (being born before 37 weeks gestation)