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Parvovirus B19

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Overview

Parvovirus B19 (from Latin ‘parvus’ meaning small) is a small, single-stranded DNA virus that is spread through respiratory droplet secretion, via the placenta from a mother to the foetus, and via blood transfusion.

It can lead to a range of clinical problems, namely ‘slapped-cheek syndrome’, erythema infectiosum, or fifth disease in children. Other conditions include pancytopenia, aplastic crises, and hydrops fetalis.

Pathophysiology

Parvovirus is spread via respiratory droplets, via the placenta, or through blood transfusion. It targets rapidly growing red blood cell progenitors which are found in the bone marrow, foetal liver, umbilical cord, and peripheral blood.

This can lead to decreased erythropoiesis in individuals with pre-existing increased strain on the bone marrow (such as sickle-cell disease, thalassaemia, hereditary spherocytosis, and haemolytic anaemias. This temporary decrease can cause an aplastic crisis, where there is a halt in red blood cell production.

Suppression of erythropoiesis in the developing foetus can lead to severe foetal anaemia and hydrops fetalis, increasing the risk of miscarriage and stillbirth.

Epidemiology

  • The precise incidence is not known
    • Around 15% of preschool children, 50% of children aged 15 years, and 60% of adults have serological evidence of past infection
  • Infection is most common in children aged 6-10 years but can happen at any age
  • Seasonal outbreaks occur every 3-4 years, mainly in late winter and early spring

Presentation

Parvovirus B19 infection presents with an acute biphasic illness with a facial rash resembling a ‘slapped cheek’:

  • Prodromal symptoms – around 1 week after exposure and 1-2 days before rash:
  • Facial rash – usually develops as the child starts to feel better
    • The rash is erythematous, and macular, and appears on one or both cheeks – ‘slapped cheek’
  • Other features:
    • Maculopapular rash – may develop 1-4 days after the initial rash spreading to the torso and extremities. This is reticular in appearance and lasts 1-3 weeks

Investigations

Overview

In healthy children and adults, the diagnosis can be made clinically.

If a pregnant person has suspected parvovirus B19 infection, contact a specialist immediately (e.g. the local infectious diseases department).

Management

Overview

For children and non-pregnant adults, treatment is supportive. Exclusion from school is not necessary once the rash occurs as patients are not infectious 1 day after the presence of a rash.

For pregnant people, if parvovirus B19 infection is suspected or there is possible exposure, contact a specialist immediately. This is discussed more in Parvovirus B19 Exposure in Pregnancy.

Complications

  • Complications in pregnancy:
    • Hydrops fetalis
    • Foetal loss
    • Maternal pre-eclampsia-like syndrome (mirror syndrome)
  • Aplastic anaemia/aplastic crisis:
    • Particularly in those with increased bone marrow strain such as sickle-cell disease, thalassaemia, hereditary spherocytosis, haemolytic anaemias
  • Neurological complications:

Prognosis

  • Parvovirus B19 is mild, self-limiting, and usually resolves within 1-3 weeks with lifelong immunity
  • In pregnant people with confirmed parvovirus B19 infection, the prognosis depends on gestational age. This is discussed more in Parvovirus B19 Exposure in Pregnancy.

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