Parainfluenza Virus 1, 2, 3

 

Clinical Background

Parainfluenza viruses (PIV) are the second most common cause of acute upper and lower respiratory tract infections (URI and LRTI) in the U.S. for children younger than 5 years.

Epidemiology

  • Prevalence
    • PIV causes 65% of croup cases, 20-40% of LRTIs and 20% of URIs in preschool children
    • 3/1000 cases of croup require medical attention per year
  • Age – usually in children 3-5 years
  • Transmission – via respiratory droplet

Classification

  • PIV types 1, 2, and 3 are clinically the most common
    • Types 1 and 2 are the primary causes of laryngotracheobronchitis (croup)
      • Seasonal biennial outbreaks in the U.S., currently occurring in the fall of odd-numbered years
    • Types 1 and 3 are common in early childhood, causing localized outbreaks in nurseries, schools, orphanages, and pediatric wards
    • Type 3 is second only to respiratory syncytial virus (RSV) as a cause of bronchiolitis and pneumonia in infants
      • Can cause parotiditis similar to mumps
      • Peak is late spring
    • PIV type 4 is less well-studied but also causes URI and LRTI

Organism

  • An enveloped and single-stranded RNA virus belonging to the Paramyxoviridae family
  • Other viruses in this family include RSV, mumps, measles, metapneumovirus (hMPV), Hendra and Nipah viruses

Clinical Presentation

  • May present as mild upper respiratory illness, croup, bronchiolitis or pneumonia
    • Older children and adults tend to have milder disease

Treatment

  • Treatment is symptomatic and supportive.