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 

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

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