STX2 and hemolytic-uremic syndrome: It has been hypothesized [8] that the AAF/I augment adherence of EHEC O104:H4 to the intestinal epithelium, a process that facilitates systemic absorption of Stx2a, the major EHEC virulence factor involved in the pathogenesis of HUS [19]–[21] and the major virulence factor of the outbreak strain in animal models [22].