- Family Parvoviridae
- Genus Erythroparvovirus
- Nonenveloped, icosahedral capsid, and linear single-stranded DNA genome
- Very small: approximately 22–24 nm in diameter
- Discovered in 1974
- Unable to propagate virus in cell cultures
- Unique tropism for human erythroid progenitor cells
Epidemiology and Pathogenesis
- Infection occurs at all ages, but it is more common in children 3–15 years of age.
- Outbreaks commonly occur in schools and childcare settings and are more frequent between late winter and early summer.
- 90% of patients ≥ 60 years old are seropositive.
- Parvoviruses commonly cause disease in animals and insects.
- B19 is the only human parvovirus pathogen.
- Infected respiratory droplets
- The secondary attack risk for exposed household members is 50% and for classroom contacts 25%.
- Life cycle of B19: Virus binds to host cell receptors → endocytosis → translocation of genome to host nucleus → DNA replication → RNA transcription → assembly of capsid and packaging of genome → cell lysis with release of mature virions
- Initial infection with B19 at site of entry (usually upper respiratory tract) → spreads to rapidly dividing erythroid precursor cells in bone marrow, which express a P blood antigen
- Once inside host cell, viral DNA enters nucleus → virus is cytotoxic to cells → ↓ erythrogenesis:
- B19 requires P blood antigen receptor to enter cell.
- Rare individuals who lack P antigen are immune.
Diseases Caused by Parvovirus B19
- Erythema infectiosum (5th disease): biphasic disease that occurs mainly in children
- Initial phase:
- Reflecting lytic infection
- Marked by nonspecific flu-like symptoms
- ↓ Hemoglobin levels
- Immune-mediated phase:
- Begins 2–3 weeks later
- Characterized by rash and arthralgia: “slapped cheek rash” appears first on face → spreads to arms and legs
- Diagnosis is usually based on the clinical presentation; if diagnosis is unclear, IgG and IgM antibody testing by ELISA may be required.
- Management: self-limited illness that requires only supportive treatment
- Initial phase:
- Polyarthropathy syndrome in adults may not be preceded by rash.
- Acute, symmetric joint pain
- Usually involves feet, knees, hands, and wrists
- No lasting joint damage
- Self-limiting illness; resolves in 3 weeks
- Management: symptomatic analgesia (NSAIDs) for painful joints and supportive care
Pure red cell aplasia:
- Cannot clear parvovirus B19 infections → leads to aplasia of RBCs and their precursors
- May not have classic signs of infection
- Causes chronic anemia
- Can be life threatening
- Diagnosis: PCR for parvovirus B19 detects infection.
- Aimed at reducing immunosuppression if possible (e.g., reduce chemotherapy dosage)
- Intravenous immunoglobulin (IVIG) treatment
- In severe cases, bone marrow transplantation
Patients with hemoglobinopathies
Transient aplastic crisis may result in those with hemoglobinopathies (e.g., sickle cell disease):
- Transient reticulocytopenia (7–10 days) leads to ↓ hemoglobin levels.
- Symptoms include:
- Possibly arthralgia
- Maculopapular rash
- Generally resolves in weeks
- Management: transfusion for hemoglobin < 6 g/dl with few reticulocytes
- Hydrops fetalis:
- Defined as abnormal accumulation of fluid in fetal soft tissue
- Thought to be due to acute anemia caused by virus: decrease in RBC numbers and increased need for circulating volume leads to fluid retention.
- Associated with increased risk of fetal death
- Intrauterine transfusion
- IVIG treatment
- Postnatal intubation/ventilation support and fluid management
- Fetal death in utero:
- Risk ↑ the earlier the infection is contracted during gestation.
- Immature fetal immune system is less capable of fighting infection.
- Congenital anemia:
- Fetal RBC turnover is faster than that in postnatal life.
- Makes fetus more susceptible to anemia
- Parvovirus involvement is usually identified via IgG and IgM antibody testing by ELISA.
Comparison of Common Childhood Rashes
|Number||Other names for the disease||Etiology||Symptoms||Rash description|
|1st disease||Measles virus||Maculopapular rash begins on face and behind ears → spreads to trunk/extremities|
|2nd disease||Streptococcus pyogenes|
|3rd disease||Rubella virus||Discrete macules on face → spread to neck, trunk, and extremities|
|5th disease||Parvovirus (erythrovirus) B19||Rash|
|6th disease||Human herpesvirus 6B or human herpesvirus 7|
- Heegaard, E., Brown, K. Human Parvovirus B19. Clin Microbiol Rev. 2002 Jul; 15(3): 485-505.
- Cherry, J.D., Schulte, D. J. Human Parvovirus B19. Feigin RD, Cherry JD, Demmler-Harrison GJ, Kaplan SL, eds. Feigin & Cherry’s Textbook of Pediatric Infectious Diseases. 6th ed. Philadelphia, PA: Saunders Elsevier; 2009. Vol 2: 1902-1920.
- Cennimo, D. (2019). Parvovirus B19 Infection Differential Diagnoses. Emedicine. Retrieved February 3, 2021, from: https://emedicine.medscape.com/article/961063-differential
- Jordan, J. (2019). Clinical manifestations and diagnosis of parvovirus B19 infection. UpToDate. Retrieved February 2, 2021, from: https://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-parvovirus-b19-infection
- Jordan, J. (2020) Treatment and prevention of parvovirus B19 infection. UpToDate. Retrieved February 2, 2021, from https://www.uptodate.com/contents/treatment-and-prevention-of-parvovirus-b19-infection