VTEC are a specific group of the bacterium Escherichia coli. The commonest member of this group of bacteria in Ireland is E. coli O157:H7. E. coli O26 is the next most common strain. Although most strains of E. coli are harmless and live in the intestines of healthy humans and animals, the VTEC strain produces a powerful toxin which can cause severe illness, particularly in children under five and the elderly. The infection can be passed from person to person, through consuming contaminated food or water or contact with infected animals or contamination in the environment.