Croup, characterized by a seal-sounding cough, is a condition caused by an acute viral infection in the larynx, trachea, and bronchi (hence its alternative name: laryngotracheobronchitis).
Viruses responsible for the infection include: parainfluenza (the most common factor), adenovirus, measles and respiratory syncytial virus (RSV). It causes the tissues in the upper airway to swell thus constricting the airway and causing a cough.
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