The first objective of this study is to further elucidate the role of endogenous EPO and its potential clinical relevance in HUS by measuring endogenous EPO levels in different species: human patients (infection with EHEC O104:H4, 2011 German outbreak), gnotobiotic piglets (subjected to EHEC O104:H4 or EHEC O157:H7 86-24) and mice (subjected to Stx2 derived from EHEC O157:H7 86-24). This evidence concerns the gene EPO and infection.