Erythrovirus B19 infection in humans

Erythrovirus B19 (B19) previously called parvovirus B19 is the only human p athogen in the family Parvoviridae. B19 is an autonomously replicating smal l single stranded non-enveloped DNA of 5.5 Kh with hairpin termini through which it replicates, when the cells are in the S-phase. Virus host interact ions are mediated through the capsid protein VP2 attaching to P antigen rec eptor 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 ne utralizing, 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 o r immunosuppression manifest disease, which may be persistent. In the immun ocompetent host it causes erythema infectiosum in children, arthralgia or c hronic polyarthritis especially in females, nonimmune hydrops foetalis, sev eral haematological disorders and recently fulminant hepatitis in children. The virus is transmitted through tl-le 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 d iagnosis. Viral DNA can be detected by polymerase chain reaction (PCR) or h ybridization procedures in patients's 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 V P1 and VP2 recombinant proteins as B19 vaccines are areas which need the ur gent attention of parvovirologists, epidemiologists and clinicians.