Update on HEV infections in blood donors in Germany – half of all infections are missed by current testing

In order to avoid transfusion-transmitted HEV infections, universal testing was implemented in 2020 with a minimal detection limit of 2,000 IU/mL on individual donation level to ensure the identification of high viremic donations. No definite quantification of the infectious dose has been published. Some case reports suggest that 7,000-10,000 IU HEV can be sufficient to cause clinical disease. Here we report data on HEV infections from the donor epidemiology supplemented by an estimation of the number of HEV infections missed by testing.

Data from the national blood donor surveillance included the number of HEV infections stratified for sex, age group and region. Limits of detection (LoD) were provided by the blood establishments (BE). Estimation of undetected HEV infections was made for each BE that provided an LoD using the distribution of viral loads in 1,200 blood donors published by Harvala et al. (https://doi.org/10.3201/eid2809.220487). Data on symptomatic HEV infections in the general population was used for comparative analyses

Altogether, 11,514 HEV infections were reported from 2020 to 2023 (data included until April 2024).HEV/100,000 donors ranged from 208.6 in 2021 to 280.2 in 2023. 1 in 1,470 donations was HEV-RNA-positive. Most HEV infections were identified in the age group 35-54 years and prevalence was 1,5 times higher in male than in female donors. Regional differences were found with highest incidence in Brandenburg (271/100,000) and lowest in Baden-Wurttemberg (109/100,000) resembling the distribution of reported clinical cases. We received the LoD for BE that discovered 10,1501 of the 11,514 HEV infections (88.2%). Test sensitivities ranged from 36-1,785 IU/mL. Applying the published distribution of HEV viral loads for each BE individually, the expected total number of HEV infections would have been 19,761, 1.95 times higher than the actually discovered number of infections.

From 2020 to 2023 1 in 1,470 donations had measurable HEV viremia. The calculated expected number of HEV-positive donations is nearly twice as high. Still, transfusion transmitted HEV infections steeply declined using data from passive hemovigilance but also from the donor derived lookbacks. While the currently mandated LoD for HEV testing seems justified to provide an acceptable level blood safety, the infection pressure in the general population has to be closely monitored to allow for possible adjustments.

Both authors declare no conflicts of interest.