The intestines of all humans and animals are full of microorganisms, some of which are beneficial but others are pathogenic. Bacterial pathogens such as Salmonella, Campylobacter and Escherichia coli (strain O157:H7) are common examples. Contamination of foods by faecal material is the major cause of food poisoning events. This includes indirect contamination, for example from people's hands if they prepare food without washing their hands after visiting the latrine/toilet (see below).
Escherichia coli (abbreviated to E.coli) exists in many harmless varieties or ‘strains', but some strains are pathogenic. The strain called E.coli O157:H7 causes a potentially fatal foodborne disease in humans.