Parvovirus B19

Parvovirus B19 is a non-enveloped, single-stranded DNA virus with selective tropism for rapidly dividing erythroid precursor cells due to expression of the P antigen receptor. In healthy children, infection typically presents as erythema infectiosum (fifth disease) with the characteristic erythematous 'slapped cheek' facial rash followed by a lacy, reticular rash on the trunk and extremities. The virus causes temporary cessation of red blood cell production, which is usually clinically insignificant in healthy individuals due to the long lifespan of RBCs (120 days). However, in patients with underlying hemolytic anemias (sickle cell disease, hereditary spherocytosis, thalassemia), this can precipitate a transient aplastic crisis with severe anemia requiring transfusion. In pregnant women, infection can lead to hydrops fetalis due to fetal anemia, particularly in the second trimester. Immunocompromised patients may develop chronic anemia with persistent viremia. The virus is transmitted via respiratory droplets and has seasonal peaks in late winter and spring.