Parvovirus B19 rebound outbreak 2024 and implications for blood- and plasma-product safety.

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.