– Acute viral infection of the lower respiratory tract causing respiratory distress.

Causes and Incidence

The major viral pathogens are respiratory syncytial virus and parainfluenza-3 virus. This disease affects children under 2 years of age and often is epidemic in nature. Each year 11 of every 100 children under 12 months of age are affected. Of these, 5% are hospitalized. The disease is transmitted through direct contact with respiratory secretions. The virus may live for hours on tissues, dishes, and countertops.

Disease Process

The infecting virus spreads to the medium and small bronchioles in the lower airway and attacks the epithelial cells. This causes edema of the ciliated cells, which protrude into the lumen, losing cilia and fusing with adjacent cells to form a giant cell. These cause edema of the bronchial mucosa and production of exudate, resulting in partial obstruction and trapping of air in the alveoli.


The illness is usually preceded by an upper respiratory infection, followed by rapid onset of respiratory distress with tachypnea, tachycardia, and a hacking cough. As the disease advances, deepening chest retractions and audible wheezing, lethargy, vomiting, and dehydration develop.

Potential Complications

Atelectasis and pneumonia are common complications. Respiratory failure is also possible.

Diagnostic Tests

Definitive diagnosis is made by isolating the virus, or by immunofluorescence or enzyme-linked immunosorbent assay (ELISA).


Surgery – None.

None; ribavirin is experimental; vaccine IVIG is in clinical trials.

Oxygen mist, vaporizer, adequate fluid intake, rest.