acute laryngitis and tracheitis
acute laryngotracheitis

Viral croup or acute laryngotracheitis is caused by parainfluenza virus, primarily types 1 and 2, in 75% of cases.

Others use the term more broadly, to include acute laryngotracheitis, spasmodic croup, laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis.

Spasmodic croup is caused by the same group of viruses as acute laryngotracheitis, but lacks the usual signs of infection (such as fever, sore throat, and increased white blood cell count).

Causes of upper airway obstruction, foreign body aspiration, blunt laryngotracheal trauma, penetrating laryngotracheal trauma, tonsillar hypertrophy, paralysis of the vocal cord or vocal fold, acute laryngotracheitis such as viral croup, bacterial tracheitis, epiglottitis, peritonsillar abscess, pertussis, retropharyngeal abscess, spasmodic croup.