Shigatoxigenic Escherichia coli (STEC) and verotoxigenic E. coli (VTEC) are strains of the bacterium Escherichia coli that produce either Shiga toxin or Shiga-like toxin (verotoxin). Only a minority of the strains cause illness in humans. The ones that do are collectively known as enterohemorrhagic E. coli (EHEC) and are major causes of foodborne illness.
The best known of these strains is O157:H7, but non-O157 strains also cause a significant number of ilness.
When infecting humans, they often cause gastroenteritis, enterocolitis, and bloody diarrhea and sometimes cause a severe complication called hemolytic-uremic syndrome (HUS).