Parvoviruses and blood products.

Erythrovirus B19 (B19), a small isocahedral, non-enveloped virus (18-26 nm), is a ubiquitous infection agent in industrialised countries. Depending on the infected host, B19 has a wide range of disease manifestations from asymptomatic (the majority) to severe, including persistent infection. The risk of B19 transmission by blood products is enhanced by a high virus titre in the infected donor, by pooling of a large number of donations, and by the virus's resistance to effective inactivation methods such as heat and solvent-detergent treatments. B19-DNA has been detected in single donations, in manufacture plasma pools and in plasma derivatives (clotting factors, albumin, antithrombin III and immunoglobulins) produced by different processes. B19 transmission is mostly found in patients treated with clotting factors, as shown by a higher seroprevalence in treated haemophiliacs, by the presence of B19 DNA, and by active seroconversion. Chronic B19 infection can successfully be treated with polyvalent intravenous immunoglobulins. The key role of neutralising anti-B19 antibodies and of the virus titre has been demonstrated by B19 transmission after infusion of several B19-positive plasma batches treated with solvent-detergent. Two strategies can be followed to reduce the B19 risk: (1) reducing the viral load in the manufacture plasma pool by discarding B19-DNA-positive donations; (2) developing new strong virus inactivation methods. The physico-resistant properties of B19 make it a good model for new emergent viruses capable of infecting blood products.