Parvovirus B19 (B19) is the only member of the family Parvoviridae known to be pathogenic in humans. It is a non-enveloped, icosahedral virus that contains a single stranded linear DNA genome. The virus is widespread, and manifestations of infection vary with the immunologic and hematologic status of the host. In healthy immunocompetent children, B19 is the cause of erythema infectiosum or fifth disease, an innocuous rash illness.