Viral infection that causes severe inflammation and obstruction of the upper airway

Childhood disease manifested by acute laryngotracheobronchitis (most commonly), laryngitis, acute spasmodic laryngitis, and febrile rhinitis

Incubation period about 3 to 6 days; contagious while febrile

Recovery usually complete

Occurs mainly in children ages 3 months to 5 years

Affects boys more commonly than girls

Usually occurs in late autumn and early winter

Acute spasmodic laryngitis: usually affects children between ages 1 and 3

Viral invasion of the laryngeal mucosa leads to inflammation, hyperemia, edema, epithelial necrosis, and shedding.

This leads to irritation and cough, reactive paralysis and continuous stridor, or collapsible supraglottic or inspiratory stridor and respiratory distress.

A thin, fibrinous membrane covers the mucosa of the epiglottis, larynx, and trachea. (See How croup affects the upper airways, page 70.)

Adenoviruses

Allergies

Bacteria (pertussis and diphtheria)

Influenza viruses

Measles viruses

Parainfluenza viruses

Respiratory syncytial virus (RSV)

Rhinorrhea

Use of accessory muscles

Nasal flaring

Barklike cough

Hoarse, muffled vocal sounds

Inspiratory stridor

Diminished breath sounds

Symptoms worse at night