Hematologic and hematopoietic consequences of B19 parvovirus infection.

In hybridization experiments, B19 shows some reactivity with autonomous rodent parvoviruses but none with adenoassociated virus sequences; its termini are more closely related to adenoassociated virus than to autonomous parvoviruses. B19 shares with all parvoviruses regions of conserved homology in the left side of the genome. The absence of an internal promoter and its unusual pattern of transcription sets B19 apart from both dependent and autonomous parvoviruses. Although clearly an autonomous parvovirus, in its extraordinary fastidious behavior B19 resembles a dependent parvovirus, capable of replication only in the special nuclear milieu of terminally differentiating erythroid cells. Adaptations at the molecular level may have been necessary for B19 parvovirus to acquire its high degree of specificity and low level of pathogenicity and thus succeed in human populations.