The production of verotoxins is one of the mechanisms by which Escherichia coli can produce diarrhea. First associated with hemorrhagic colitis and hemolytic uremic syndromes, the so-called verotoxin-producing Escherichia coli strains (VTEC) have been shown to cause also uncomplicated watery or bloody diarrhea. They have been found both in outbreaks and sporadic cases and were isolated in all countries where they were searched for. Inadequately cooked meat of bovine origin is thought to be the first source of contamination but person-to-person transmission has also been demonstrated. Until now most studies focused on serotype O157:H7, easy to detect thanks to its rare biotype. However a screening by PCR confirmed by VTEC strain isolation and cytotoxicity testing showed that in Belgium only 18% of VTEC strains belong to this serotype.