West Nile Virus preparedness plan to ensure safe blood components in Switzerland: a risk-based approach

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 Methods The 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 WNVRNA-positive case would be detected every 11 years. With 100 WNVME cases per year, approximately 8 8 donations would be detected every year. The additional cost burden of introducing WNV-NAT in Switzerland is 2 6 million euros per year. Costs to prevent one case per year are thus between 27 million and 0 28 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. Conclusions The 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.