parainfluenza virus

Parainfluenza viruses are single-stranded, negative-sense RNA viruses belonging to the Paramyxoviridae family. There are four main serotypes (PIV-1 through PIV-4), with PIV-3 being the most common cause of lower respiratory tract infections in infants and young children. PIV-1 is the classic cause of croup, characterized by the distinctive 'barking' cough and inspiratory stridor due to laryngeal and subglottic inflammation and edema. The virus spreads via respiratory droplets and has a 2-6 day incubation period. Clinical manifestations range from mild upper respiratory symptoms to severe lower respiratory tract disease, particularly in immunocompromised patients. PIV infections are more common in fall and winter months. Diagnosis can be confirmed through viral culture, RT-PCR, or direct fluorescent antibody testing. Treatment is primarily supportive, though severe cases may benefit from nebulized epinephrine or corticosteroids for airway inflammation.