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Background: Since the beginning of 2024, several European countries reported unusually high numbers of Human parvovirus B19 (B19V) infections. An increase in B19V incidence rate might have implications for blood products for direct transfusion, however, large data sets for analysis of this outbreak are missing., Study Design and Methods: B19V nucleic acid testing (NAT) of plasma donations collected between June 2018 and May 2024 from mainly Central European countries (n = 9.6 million) and the United States (n = 70.7 million) was done to the individual donation level., Results: In Central Europe, there was a marked increase in B19V incidence from November 2023 onwards, which peaked in April 2024 with a 33-fold higher than average B19V incidence versus before the COVID-19 pandemic. In the United States, a similar trend was seen, with a yet still 6-fold lower increase than in Europe at the same time. The largest increase in B19V positivity was seen in the youngest plasma donor cohort., Discussion: A B19V infection gap during the COVID-19 pandemic is likely the basis for the rebound outbreak in 2023/2024, particularly in Europe. B19V NAT of millions of plasma donations provides for large scale numbers to solidify available epidemiology insight, and to support adequate risk assessments. Based on the situation it may be prudent to consider B19V NAT for blood components specifically directed towards transfusion to higher risk recipients, or alternatively, preselecting B19V seropositive individuals or advanced age donors at higher likelihood of seropositivity and thus lower risk of virus transmission., (© 2024 The Author(s). Transfusion published by Wiley Periodicals LLC on behalf of AABB.)

Background: Human parvovirus B19 (B19V) is a highly prevalent pathogen, and plasma pools for manufacturing of plasma-derived products have been shown to contain antibodies against B19V (B19V immunoglobulin G [IgG])., Study Design and Methods: The megakaryoblastic cell line UT7/Epo-S1 can be infected with B19V Genotype 1 and as demonstrated here by immunocytochemistry, Western blot, and reverse transcription-polymerase chain reaction (RT-PCR) of B19V-specific mRNA, also with the more recently discovered Genotype 2. Based on B19V RT-PCR analysis of infected UT7/Epo-S1 cells, an infectivity assay was established and implemented for a B19V neutralization assay. To investigate the role of B19V neutralization in relation to B19V IgG titers, more than 1,000 manufacturing plasma pools were tested by enzyme-linked immunosorbent assay., Results: Plasma pools were found to contain a mean B19V IgG titer of 33 +/- 9 IU per mL, with the lowest titer at 11 IU per mL. These 11 IU per mL B19V IgG neutralized 4.6 log B19V Genotype 1 and greater than 3.9 log Genotype 2 infectivity. Accordingly, a 10 percent intravenous immunoglobulin (IVIG) product prepared from such pools was found to contain an even higher B19V neutralization capacity., Conclusion: A high capacity of B19V Genotypes 1 and 2 neutralization was demonstrated in plasma pools for fractionation, an inherent feature based on the constantly high titer of B19V IgG in these pools. The neutralizing activity of B19V IgG was shown to be maintained in the 10 percent IVIG product tested.