Infections with SEOV are likely to be missed in France, either because hantavirus infection is rarely suspected outside the PUUV endemic area (North-Eastern France), or because most of the public hospital or private clinical laboratories in France use commercial kits for hantavirus serologic diagnosis directed against PUUV (POC Puumala IgM rapid test [Reagena, Toivala, Finland]). This evidence concerns the gene CD40LG and infection.