Long-Term Retrospective Analysis of Parvovirus B19 Infections in Blood Donors (2012–2024): Significant Increase in Prevalence Following the SARS-CoV-2 Pandemic

Background/Objectives: Parvovirus B19 (B19V) is a non-enveloped single-stranded DNA virus transmissible by blood transfusion, with potentially severe outcomes in immunocompromised and pregnant recipients. In this study, we investigated the B19V prevalence in 441,084 blood donations from Salzburg, Austria, collected between 2012 and 2024, focusing on changes in epidemiological dynamics before, during, and after the SARS-CoV-2 pandemic. Additionally, the B19VB19V persistence and its implications for deferral policies were assessed. Methods: Donor samples were screened for B19VB19V DNA by qPCR (2012–2024) and for SARS-CoV-2 total anti-N antibodies (2020–2024). B19VB19V prevalence rates, cycle threshold (Ct) values, and seasonal distribution were compared between pre-pandemic, pandemic, and post-pandemic phases. Follow-up testing of initially B19VB19V-positive donors was performed after a 2-year deferral period. Results: The B19VB19V positivity rate of 0.13% (2012–2019) significantly decreased to 0.02% during the SARS-CoV-2 pandemic (2020–2022). A substantial increase occurred post-pandemic, with prevalence reaching 1.47% in 2024. Significant lower Ct values were observed in the post-pandemic phase, indicating higher viral loads. Additionally, younger donors (aged 18–45 years) showed significantly lower Ct values. After a 2-year deferral, 39% of re-tested donors remained B19VB19V DNA-positive. Conclusions: B19VB19V circulation increased substantially after the SARS-CoV-2 pandemic. Our observation is consistent with international reports and is likely due to an ‘immunity debt’ that has been accumulated due to pandemic-related public health interventions. Targeted B19VB19V screening and strict deferral strategies may be warranted particularly during outbreak periods to protect high-risk transfusion recipients.