Changes in Parvovirus B19 positivity rates in plasma units for fractionation: an unexpected effect of non-pharmaceutical interventions against COVID-19? – Sauleda – – Vox Sanguinis

Parvovirus B19 (B19) is a small non-enveloped DNA virus, discovered in 1975 by Yvonne Cossart in the blood of a healthy blood donor. Although infection with B19 is usually mild in children and adults, some people may develop severe arthropathy and a transient aplastic crisis which, in immunocompromised patients, may progress to persistent erythrocyte aplasia requiring transfusion. Respiratory droplets spread B19, and it is highly infectious [1]. The number of copies of B19 DNA is often greater than 10ten copies / ml, and transmission through blood components and plasma-derived drugs has also been documented [2]. The European Pharmacopoeia stipulates that the concentration of B19 in manufacturing plasma pools should not exceed a concentration of 104 IU / ml [3].

In our regional blood bank in Catalonia (Spain), units of plasma obtained from donated whole blood and plasma apheresis are sent to the fractionation industry, where the units are tested for B19 DNA. B19 infections follow a seasonal pattern in plasma donors, with most positive plasma units corresponding to donations obtained between March and July [1]. From 2014 to 2019, we were informed of 256 positive plasma units for B19 (Figure 1). However, between January 2020 and July 2021, the plasma fractionator reported only three units of plasma positive for B19, from three whole blood donors, one man and two women who donated on January 18 and on January 17 and 28. February 2020. Within 16 months, no more B19 infections were reported among the 314,898 units of plasma sent for fractionation. There are significant differences when comparing the annual B19 positivity rates between 2014-2019 and 2020-2021 (Figure 1). The plasma fractionator confirms that there has been no change in the screening policy for B19.

Annual trends in B19 positivity rates in plasma units. The bars represent the number of B19 positive units and the line represents the B19 positive units per 100,000 plasma units sent for fractionation. The 95% confidence intervals (CI) for B19 positivity per 100,000 plasma units are: 9.91–20.71 in 2014, 28.06–45.64 in 2015, 6.27–15.48 in 2016, 8.66–18.78 in 2017, 11.13–22.46 in 2018, 24.79–42.97 in 2019, 0.29 to 4.05 in 2020 and 0.00 to 0.00 in 2021 (Clopper-Pearson 95% CI)

On March 11, 2020, the World Health Organization declared COVID-19 a pandemic, and a few days later the lockdown was implemented in Spain until the end of May 2020. Non-pharmaceutical interventions (NPI), such that social distance and the obligatory mask outside and inside have been maintained until very recently. Wearing a face mask is always mandatory inside public buildings including schools, public transport and outdoors when physical distance is not possible. Although plasma donors with a low viral load may have been missed by B19 screening, the continued absence of high viral load infections in plasma donors for more than a year supports an association with the use of NPI. In Europe, seasonal influenza activity in 2020 was very low, also probably due to prolonged use of NPI [4].

In conclusion, here we describe an unexpected but unsurprising effect of strict and sustained NPI in decreasing B19 infection in plasma donors in Catalonia. B19 is unusual in that it is transmitted by both droplets and transfusion. Therefore, this finding may enhance the utility of NPI if a future pandemic agent emerges.


The authors did not disclose any conflict of interest.

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