Erythrovirus B19 infection in humans.

Erythrovirus B19 (B19) previously called parvovirus B19 is the only human pathogen in the family Parvoviridae. B19 is an autonomously replicating small single stranded non-enveloped DNA of 5.5 Kb with hairpin termini through which it replicates, when the cells are in the S-phase. Virus host interactions are mediated through the capsid protein VP2 attaching to P antigen receptor expressed on certain host cells, which imparts narrow host and tissue tropism. It affects the progenitor red cells, megakaryoblast, endothelial cells and a few organs like the kidney and the heart. VP1 antibodies are neutralizing, non-structural protein NS-1 exert cell cytotoxicity while NS-2 regulates replication. The virus is present world-wide. Most infections are asymptomatic but individuals with red cell defect, immune system defects or immunosuppression manifest disease, which may be persistent. In the immunocompetent host it causes erythema infectiosum in children, arthralgia or chronic polyarthritis especially in females, nonimmune hydrops foetalis, several haematological disorders and recently fulminant hepatitis in children. The virus is transmitted through the upper respiratory tract by droplets, transfusion of blood or its components (factor VIII) and transplacentally. The incubation period is 6-11 days after intranasal inoculation, in human volunteers. Detection of IgM antibodies is most important in serological diagnosis. Viral DNA can be detected by polymerase chain reaction (PCR) or hybridization procedures in patients sera or infected tissues. Intravenous immunoglobulin can be used in the treatment as well as in prophylaxis. In view of its increasing association with a wide variety of clinical diseases, a closer look in its biology, host virus interactions and evaluation of VP1 and VP2 recombinant proteins as B19 vaccines are areas which need the urgent attention of parvovirologists, epidemiologists and clinicians.