STEC strains positive for the subtypes stx2a, stx2c, or stx2d were found to be associated with an enhanced virulence and with the development of the HUS in humans (Friedrich et al., 2002; Beutin et al., 2004; Bielaszewska et al., 2006; Persson et al., 2007). The gene discussed is STX2; the disease is hemolytic-uremic syndrome.