Parainfluenza Virus 1, 2, 3, 4


Indications for Testing

  • Flu-like illness during parainfluenza virus (PIV) season

Laboratory Testing

  • Clinical features and diagnosis of parainfluenza viruses (CDC)
  • Clinical diagnosis usually suffices
  • Direct fluorescent antibody (DFA) – rapid testing; may be useful during epidemics to rule out influenza
    • Nasopharyngeal aspirates for viral testing of specimens
    • Consider DFA for all of the following concurrently – influenza, adenovirus, RSV, and hMPV
    • Less sensitive than culture, polymerase chain reaction (PCR)
  • PCR – most sensitive; some assays can detect parainfluenza 4
  • Sequential panel antibody testing
    • Supports diagnosis
    • Cross reactivity can occur with assays for IgG, particularly due to mumps virus
    • Usually not necessary, except possibly during epidemic events
  • Viral culture – gold standard
    • Conventional culture requires up to 7 days
    • Rapid culture requires less time (24-48 hours)
  • Consider additional testing for other atypical/bacterial organisms
  • CBC – may be helpful in moderately to severely ill patients if differential diagnosis includes bacterial disease


  • Chest x-ray – rule out pneumonia in moderately ill patients

Differential Diagnosis

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 <5 years.


  • Prevalence
    • PIV cause 65% of croup cases, 20-40% of LRTIs and 20% of URIs in preschool children
    • 3/1,000 cases of laryngotracheobronchitis (croup) require medical attention per year
  • Age – usually children 3-5 years
  • Transmission – respiratory droplet


  • PIV types 1, 2, and 3 – clinically the most common
    • Types 1 and 2 – primary causes of croup
      • Seasonal biennial outbreaks in the U.S. – currently occurring in the fall of odd-numbered years
    • Types 1 and 3 – common in early childhood; causes localized outbreaks in nurseries, schools, orphanages, pediatric wards
    • Type 3 – 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
    • Type 4 – less well-studied but also causes URI and LRTI


  • Enveloped, 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

Indications for Laboratory Testing

  • Tests generally appear in the order most useful for common clinical situations
  • Click on number for test-specific information in the ARUP Laboratory Test Directory
Test Name and Number Recommended Use Limitations Follow Up
Respiratory Viruses DFA with Reflex to Viral Culture, Respiratory 0060281
Method: Direct Fluorescent Antibody Stain/Cell Culture

Confirm presence of specific viral etiology for disease

Sensitivity of DFA methodology is dependent on the adequacy of the specimen

Parainfluenza 1-4 by RT-PCR 2006247
Method: Qualitative Polymerase Chain Reaction

Most sensitive test for detecting parainfluenza 1-4

Viral Culture, Respiratory 2006499
Method: Cell Culture

Viruses that can be isolated – adenovirus; CMV; enterovirus; HSV; influenza A and B; parainfluenza types 1, 2, and 3; RSV; and VZV

Virus-specific tests are recommended

Slow growth; not ideal for acute identification

Respiratory Viruses Rapid Culture 2001504
Method: Cell Culture/Immunofluorescence

Isolate respiratory viruses, including influenza A and B, adenovirus, RSV, and parainfluenza types 1, 2, 3

Other viruses such as HSV or CMV are not routinely detected in this culture

Decreased sensitivity for detection of adenovirus

Human metapneumovirus is not detected

Additional Tests Available
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
CBC with Platelet Count and Automated Differential 0040003
Method: Automated Cell Count/Differential

Aid in differentiating between bacterial and viral illness

Respiratory Viruses DFA 0060289
Method: Direct Fluorescent Antibody Stain

Recommended for detecting parainfluenza virus in specimens other than CSF

Viral Culture, Respiratory and Cytomegalovirus Rapid Culture 2006497
Method: Cell Culture/Immunofluorescence

Viruses that can be isolated – adenovirus; CMV; enterovirus; HSV; influenza A and B; parainfluenza types 1, 2, and 3; RSV; and VZV

Virus-specific tests are recommended