Parvoviruses

Excerpt

The parvoviruses (parvo meaning small) are a group of very small DNA viruses that are ubiquitous and infect many species of animals. The small amount of DNA contained in the viruses does not carry sufficient genetic information to direct its own replication in host cells. As a result, parvoviruses have unusual requirements for replication, such as a simultaneous helper virus or rapidly dividing cells. They are divided into two groups on the basis of these requirements. The parvoviruses that multiply only in cells coinfected with a helper adenovirus constitute the genus dependovirus (previously called the adeno-associated viruses [AAVs]). These viruses have not been shown to cause disease in humans. The second group of parvoviruses, constituting the genus Parvovirus, do not require a helper virus for replication. However, they multiply only in cells that are in the process of replicating their own DNA. The diseases caused by autonomous parvoviruses reflect their requirement for actively dividing cells. The human autonomous parvovirus, B19 virus, replicates in erythroid precursor cells and hence produces aplastic crisis in predisposed individuals with underlying hemolytic anemia or immunodeficiency. Other clinical manifestations of B19 virus infection are due to the host immune response to the virus.