Outbreaks in primary school children are classically in the winter and spring. Joint involvement may occur. Children with shortened red cell survival can develop profound anemia (aplastic crises). Infection during pregnancy can lead to hydrops fetalis.
Caused by erythrovirus (formerly parvovirus) B19, spread by droplet infection. The first sign of infection is usually marked erythema of the cheeks (slapped cheek appearance) often with relative circumoral pallor. 1 to 4 days after the slapped cheeks an itchy, erythematous, maculopapular rash develops on the trunk and limbs. As the rash on the limbs clears it leaves a lacy, reticular pattern. The rash may fluctuate over the next 1-3 weeks and a hot bath, for example, may lead to recrudescence of an evanescent rash.