What is the role of parainfluenza virus (PIV) in the etiology of viral pneumonia?

Updated: Mar 24, 2021
  • Author: Zab Mosenifar, MD, FACP, FCCP; Chief Editor: John J Oppenheimer, MD  more...
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Answer

Parainfluenza virus (PIV) is a common virus that infects most persons during childhood. PIV is second in importance to only RSV in causing lower respiratory tract disease in children and pneumonia and bronchiolitis in infants younger than six months. Transmission is through direct person-to-person contact or large-droplet spread.

PIV is characterized by nucleocapsids, which develop in the cytoplasm of infected cells, with hemagglutinin present in the virion envelope.

There are four subtypes of PIV, based on antigenic characteristics. PIV type 3 is endemic year-round, while types 1 and 2 peak during the fall season. Immunity is short term, and recurrent upper or lower respiratory tract infections occur throughout life. The infections vary from a mild illness to life-threatening croup, bronchiolitis, or pneumonia. Infection in immunocompromised hosts can result in life-threatening pneumonia with lung injury and respiratory failure. In one study, 44% of hematopoietic stem cell transplant (HSCT) patients with PIV progressed to develop pneumonia, of which 37% died. [20]


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