• Member of the Family Paramyxoviridae (which includes human mumps, measles, parainfluenza (PIV), respiratory syncytial virus (RSV) and metapneumovirus), Genus Paramyxovirus (includes parainfluenza serotypes 1-4 and mumps viruses).
• Relatively large particles with negative sense, single-stranded RNA in a helical nucleocapsid surrounded by a pleomorphic envelope. Unlike Influenza viruses, they do not have a segmented genome.
• Worldwide distribution; seasonal, occurring predominantly in Spring-Fall, unlike Influenza which predominates in the winter.
• Parainfluenza 1 and 2 are second only to RSV as an important cause of severe respiratory disease in infants and young children, especially croup. In adults, PIV generally causes mild upper respiratory infections, but can result in more severe disease in the elderly and immunocompromised patients.
• Transmitted by direct contact with respiratory secretions (hands, objects, surfaces) or large aerosol particles (coughing/sneezing).
• Initial infection is of the epithelial cells of the nose and oropharynx with distal spread to ciliated and alveolar cells of the small and large airways.
• Entry into respiratory epithelial cells via hemagglutinin-neuraminidase glycoprotein (HN) attachment to sialic acid cell membrane receptors, with viral – cell membrane fusion mediated by the fusion glycoprotein (F). Viral replication occurs in the cell cytoplasm.
• Induces cell to cell fusion of adjacent infected cells, resulting in multi-nucleated giant cells.
• The HN and F surface proteins are major antigenic targets of neutralizing antibody.
• The Incubation period is 2-7 days. Upper and lower respiratory tract infection primarily in children.
• Symptoms are generally “cold-like”, however, may also present as bronchitis, croup or pneumonia.
• Infection is limited to the respiratory tract, no systemic symptoms.
• Direct detection of parainfluenza genome in nasal washings and respiratory secretions by PCR assay (preferred diagnostic test).
• Direct detection of PVI antigen in respiratory secretions (less sensitive than PCR).
• Viral culture: detection of hemagglutination-positive virus after 2-14 days cultivation of respiratory secretions.
• Serology: not practical
Differential Diagnosis: other respiratory viruses
• No specific anti-viral therapy available, supportive care only.
• As The host immune response may play a significant role in the pathogenesis, anti-inflammatory agents may be required for more severe disease.
Prevention and Control:
• No effective vaccine is currently available.
• Hand hygiene and respiratory etiquette.