Parvovirus B 19 - Parvo

Parvovirus B 19 - Parvo

 

Parvovirus B 19 is a member of the Erythrovirus family, so named because of its tropism for erythroid precursor cells.

Epidemiology

  • Prevalence
    • 15% of preschool children seropositive
    • 50% of young adults seropositive
    • 85% of elderly seropositive
  • Age – peak 5-15 years
  • Transmission
    • Via respiratory droplet
    • Blood products
  • Peak incidence – late winter, early spring

Organism

  • Small, single-stranded DNA virus
  • Lacks lipid envelope, so it is resistant to heat and detergent inactivation
  • Targets rapidly growing erythroid progenitor cells

Risk Factors

  • Immunodeficiency disorder
  • Pregnancy

Clinical Presentation

  • Many parvovirus (PV) infections are asymptomatic, particularly in children
  • Erythema infectiosum (EI) or fifth disease
    • Classically presents in school-aged children
    • EI is a benign, self-limited, febrile illness associated with a slapped cheek appearance on the face and a lacy or reticular rash on the trunk and limbs
  • Severe anemia is the major complication due to the virus predilection for red cell precursors in the bone marrow
    • May cause aplastic crisis or persistent chronic anemia in immunocompromised patients
  • A migratory polyarthropathy may occur in up to 50% of adults, particularly females
  • Pregnant females – abortion or stillbirth due to hydrops fetalis
  • Associated with the onset of autoimmune disorders
    • System lupus erythematosus (SLE)
    • Rheumatoid arthritis (RA)
    • Systemic vasculitides 
    • Autoimmune thrombocytopenia
    • Hemolytic anemia 

Diagnosis

  • Indications for testing – typical presentation (either rash or arthritis) in pregnant females; development of aplastic anemia in immunocompromised patient
  • Laboratory testing
    • Antibody testing
      • By the time rash or polyarthropathy occurs in immunocompetent patients, viremia is usually cleared and serum antibodies can be used to confirm the clinical diagnosis
      • Appearance of an IgM antibody response normally occurs 7-14 days after the onset of disease
      • Past infection documented by IgG antibodies
    • PCR testing
      • More sensitive than antibody testing
      • In serum samples, positive result indicates ongoing acute or persistent infection
      • In bone marrow samples, positive result indicates acute or remote infection

Treatment

  • Treatment is symptomatic
  • Prophylactic immunoglobulin can be used in pregnant and immunocompromised patients
  • Weekly monitoring in utero for hemolysis required in parvo-exposed pregnant women

See Also