Indications for Testing

• Flu-like illness during PIV season

Laboratory Testing

• Clinical diagnosis usually suffices
• Direct fluorescent antibody (DFA) – rapid testing; may be useful during epidemics to rule our 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

Imaging

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

Differential Diagnosis

• Adenovirus
• Bordetella pertussis (whooping cough)
• Chlamydia pneumoniae
• Enterovirus
• Influenza
• hMPV
• Mycoplasma pneumoniae
• RSV

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.

Epidemiology

• 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

Classification

• PIV types 1, 2, and 3 are 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, and 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

Organism

• An 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

Treatment

• Treatment is symptomatic and supportive

Tests generally appear in the order most useful for common clinical situations

General

• Crowe JE Jr, Williams JV. Immunology of viral respiratory tract infection in infancy. Paediatr Respir Rev. 2003; 4 (2) :112-119.PubMed
• Henrickson KJ. Parainfluenza viruses. Clin Microbiol Rev. 2003; 16 (2) :242-264.PubMed
• Moscona A. Entry of parainfluenza virus into cells as a target for interrupting childhood respiratory disease. J Clin Invest. 2005; 115 (7) :1688-1698.PubMed
• Ruuskanen O, Lahti E, Jennings LC, Murdoch DR. Viral pneumonia. Lancet. 2011; 377 (9773) :1264-1275.PubMed
• Sato M, Wright PF. Current status of vaccines for parainfluenza virus infections. Pediatr Infect Dis J. 2008; 27 (10 Suppl) :S123-S125.PubMed
• Weinberg GA. Parainfluenza viruses: an underappreciated cause of pediatric respiratory morbidity. Pediatr Infect Dis J. 2006; 25 (5) :447-448.PubMed

Adenovirus
Bordetella pertussis
Chlamydophila pneumoniae or psittaci
Cytomegalovirus
Enterovirus
Hantavirus
Influenza Virus
Legionella pneumophila
Metapneumovirus
Mycoplasma pneumoniae
Respiratory Syncytial Virus
Respiratory Viruses