E. coli O157:H7 is a virulent strain of E. coli with multiple genes coding for virulence. It expresses a Shiga like A/B5 toxin that behaves in a manner similar to ricin within the body. It also codes for special Pili known as H7 pili which enables it to attach to the Jejunum, an area of the GI tract that E. coli typically does not attach to.