<b><i>Introduction:</i></b> Screening of hepatitis B surface antigen (HBsAg) and individual-donation nucleic acid amplification testing (ID-NAT) of blood donors have become standard to detect hepatitis B virus (HBV) infection. However, there is still a residual risk of HBV transmission by blood components of donors suffering from occult HBV infection (OBI). Therefore, many countries implemented universal testing of anti-HBV core antigen (anti-HBc) antibodies in order to increase blood safety. In Switzerland, anti-HBc testing is not part of the routine blood donor-screening repertoire. Therefore, we sought to assess prevalence of donors with OBI in a Swiss blood donor collective. <b><i>Methods:</i></b> Blood donations were prospectively investigated for the presence of anti-HBc antibodies during two time periods (I: all donors, March 2017; II: first-time donors only, April 2017 until February 2018). Anti-HBc-positive findings were confirmed by an anti-HBc neutralization test. Discarded plasma samples of anti-HBc-confirmed positive donors were ultracentrifuged and subsequently retested by regular HBV-ID-NAT to search for traces of HBV. <b><i>Results:</i></b> During time period I, 78 (1.6%) individuals out of 4,923 donors were confirmed anti-HBc-positive. Sixty-nine (88%) anti-HBc-positive samples were available and processed by ultracentrifugation followed by repeat HBV-ID-NAT. Four samples (5.8%) were found positive for HBV DNA. Sixty-five (94.2%) samples remained HBV NAT-negative upon ultracentrifugation. During time period II, 56 (0.9%) donor samples out of 6,509 exhibited anti-HBc-confirmed positive. Fifty-five (98%) samples could be reassessed by HBV-ID-NAT upon ultracentrifugation. Three (5.5%) samples contained HBV DNA and 52 (94.5%) samples remained HBV NAT-negative. <b><i>Conclusion:</i></b> Overall, we detected 7 viremic OBI carriers among 11,432 blood donors, which tested negative for HBV by standard HBV-ID-NAT and HBsAg screening. In contrast, OBI carriers showed positive anti-HBc findings which could be confirmed in 83.8% of the cases. Thus, OBI might be missed by the current HBV screening process of Swiss blood donors. We suggest to review current HBV screening algorithm. Extended donor screening by anti-HBc testing may unmask OBI carriers and contribute to blood safety for the recipient of blood products.

Background In 2012, the Swiss Transfusion SRC founded a working group to develop a WNV preparedness plan for Switzerland in order to deal with expanding spread of WNV epidemics in Europe. Materials and MethodsThe risk estimates were computed for various presumptive incidence scenarios and brought into relation to cost estimates for the introduction of a routine WNV-NAT screening programme. The costs to prevent one case per year and the number of donations which need to be tested to detect a WNV-RNA-positive donation were calculated.Results With a theoretical postulated incidence of one West Nile virus meningoencephalitis (WNVME) case in Switzerland per year, approximately one WNV-RNA-positive case would be detected every 11 years. With 100 WNVME cases per year, approximately 8Á8 donations would be detected every year. The additional cost burden of introducing WNV-NAT in Switzerland is 2Á6 million euros per year. Costs to prevent one case per year are thus between 27 million and 0Á28 million euros, depending on the incidence assumption. Due to the geographical situation in Switzerland, it was decided to determine two potential risk regions, the southern part of the country and the remaining northern part. In addition, two risk levels and respective measures were defined. ConclusionsThe risk for WNV transmission through blood products is low even when 100 autochthonous WNV cases would be detected. With this in mind, the blood transfusion services and the national health authorities established a costefficient WNV preparedness plan to prevent WNV transfusion-transmission and maintain self-sufficiency in the blood supply.