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Microbiology · Other DNA viruses

Parvovirus B19 !

  • Virus
  • Non-enveloped (naked)
  • Droplet
  • Exam priority: medium

A tiny virus that causes fifth disease (red cheeks) in children and can cause severe anemia and harm a fetus.

Updated 2026-11-01

Also called: erythema infectiosum, fifth disease, slapped cheek syndrome

At a glance

Shape
Icosahedral, non-enveloped
Genome
Linear single-stranded DNA
Envelope
Non-enveloped (naked)
Family
Parvoviridae (genus Erythroparvovirus)
Size
About 20 to 25 nm (among the smallest viruses)

Morphology

  • The only major human single-stranded DNA virus
  • Naked, very hardy capsid

Transmission

  • Respiratory secretions
  • Transfusion of blood and blood products
  • Across the placenta, mother to fetus

Reservoir: Humans

Isolation precautions

What the care team adds to standard precautions.

Droplet
Surgical mask within about a metre; single room.

Virulence factors

  • Uses the P antigen (globoside) on erythroid precursors as its receptor
  • Kills red-cell progenitors in the bone marrow and halts erythropoiesis for some days
  • Immune complexes cause the rash and arthritis, when the patient is hardly contagious any more

Diseases it causes

Clinical picture

  • Children: red slapped cheeks followed by a lacy rash on the trunk and limbs
  • Adults, especially women: symmetric arthritis of hands, wrists and knees
  • Aplastic crisis in people with hemolytic anemia (sickle cell disease, spherocytosis, thalassemia)
  • Chronic anemia in the immunocompromised; fetal death or hydrops when infection occurs in pregnancy

Diagnosis

  • Specific IgM in immunocompetent people
  • Blood PCR in the immunocompromised and in amniotic fluid or fetal blood
  • Very low reticulocytes in aplastic crisis; giant pronormoblasts in the marrow

Treatment

There is no antiviral. Supportive care; transfusion in aplastic crisis, intravenous immunoglobulin for chronic anemia in the immunocompromised, and intrauterine transfusion for hydrops.

Drug class only; doses and regimens are set by the clinician from the current guideline.

Prevention

  • Hand and respiratory hygiene
  • Droplet precautions for aplastic crisis or chronic infection in the immunocompromised
  • Fetal ultrasound follow-up if a pregnant woman is infected

Test yourself

Think of the answer, then tap the question to see it.

Which receptor does parvovirus B19 use to infect erythroid precursors?

The P antigen (globoside) on the erythroblast membrane.

Which complication does parvovirus B19 cause in a patient with sickle cell disease?

A transient aplastic crisis, with severe anemia and almost no reticulocytes.

Why can a child with erythema infectiosum go back to school?

Because by the time the immune-complex rash appears, the contagious period is over.

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← Back to the group: Other DNA viruses

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: About Parvovirus B19 (CDC, 2024); Appendix A: Type and Duration of Precautions Recommended for Selected Infections and Conditions (CDC, 2024).

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Representative model, for educational purposes only.