​Infectious Diseases and Microbiology - Croup ( Parainfluenza viruses type 1 and 2)

​Infectious Diseases and Microbiology - Croup ( Parainfluenza viruses type 1 and 2) 
 The most common cause of croup (laryngotracheobronchitis) in newborns and early children is parainfluenza viruses (PIV) types 1 and 2. PIV is spread through direct contact with secretions or fomites, as well as breathing droplets. Immunity is ephemeral and reinfections frequent.
 
PIV 1–4 comprises the four recognized serotypes. Indicators of croup (PIV 1 and 2) include fever, barking cough, hoarseness, and inspiratory stridor. PIV 3 is linked to pneumonia and bronchiolitis in young children and babies. In both adults and children, PIV 4 causes a moderate upper respiratory infection.

 PIV damages and infects respiratory epithelial cells without spreading throughout the body. The appearance of multinucleated giant cells, a virulence factor that allows direct cell-to-cell dissemination and encourages evasion from host antibodies, is one of the histopathologic modifications.

 PIV diagnosis can be made quickly and directly by looking for the viral antigen in nasal aspirate cells. Alternatively, the virus can be isolated in cell culture and identified using PIV-specific antibodies.
 PIV does not currently have a specific treatment or vaccination.