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MCQs in Tropical Medicine

Rob Skelly DTM+H FRCP

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Answer 20

Parvovirus B19:

True a. is the causative agent of fifth disease (erythema infectiosum)
False b. was discovered after parvovirus B16
True c. antibodies are present in 70% of the UK adult population
True d. is a recognised cause of aplastic anaemia
True e. is known to cause hydrops fetalis

If confusion with human papilloma virus was to be avoided, human parvovirus could not be designated HPV. It was called virus B19. This corresponded to well B19 on a sera tray and was the location of an early isolate. There is no parvovirus B16.

Infection is asymptomatic in about 30% of cases. It is the infectious agent of fifth disease. In children the rash gives a characteristic "slapped cheeks" appearance. Incidentally unilateral slapped cheek is more commonly due to Haemophilus influenzae septicaemia.

In adults Parvovirus B19 causes a rash similar to rubella, starting on the face and spreading to trunk and then limbs. The rash is associated with antibody production. A self-limiting reactive arthritis may follow the rash, especially in adult women.

Parvovirus B19 may cause aplastic crises in sickle cell disease and in other hereditary haemolytic anaemias. It may also be responsible for refractory transfusion dependent anaemias in immunocompromised patients. The virus replicates in erythroid progenitor cells which possess the p antigen.

Symptomatic infection during pregnancy resulted in delivery of a normal child in >80% of about 200 pregnancies in a study by the PHLS. The incidence of hydrops fetalis was 10-15% and was highest in second trimester infections. There were no congenital abnomalities. Other studies in asymptomatic infection suggest the outcome may not be so good.

Copyright: Rob Skelly 2006