Definition
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. Other viruses that can cause bronchiolitis include:
The virus is transmitted from person to person by direct contact with nasal fluids, or by airborne droplets. Although RSV generally causes only mild symptoms in an adult, it can cause severe illness in an infant.
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. It is estimated that by their first year, more than half of all infants have been exposed to RSV.
Risk factors include:
- Exposure to cigarette smoke
- Age younger than 6 months old
- Living in crowded conditions
- Lack of breast-feeding
- Prematurity (being born before 37 weeks gestation)
Symptoms
Some children have infections with few or minor symptoms.
Bronchiolitis begins as a mild upper respiratory infection. Over a period of 2 - 3 days, it can develop into increasing respiratory distress with wheezing and a "tight" wheezy cough.
The infant's breathing rate may increase (tachypnea), and the infant may become irritable or anxious-looking. If the disease is severe enough, the infant may turn bluish (cyanotic), which is an emergency.
As the effort of breathing increases, parents may see the child's nostrils flaring with each breath and the muscles between the ribs retracting (intercostal retractions) as the child tries to breathe in air.
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