Course of parvovirus B19 infection

Schematic representation of the clinical course and laboratory abnormalities in normal hosts with parvovirus B19 infection. As expected for a virus that infects red cell precursors, a transient reticulocytopenia and slight drop in hemoglobin level develop during the viremic stage of infection; platelets and leukocytes (not shown) also fall during this period. Once the host mounts an immune response beginning 10 to 14 days after the infection, the viremia resolves and reticulocytes return. Note the biphasic timing of symptoms, during the peak viremia and again after the viremia has cleared. Rash, arthritis, and other symptoms typically associated with B19 occur during the second period.