Contamination is most likely to occur in raw foods, especially those of animal origin. Because of this, foods most associated with foodborne illness include:

• Poultry
• Clams, oysters and other shellfish
• Unpasteurized milk

The mixing of the products of many individual animals is also a source of danger; if any one is infected, the entire resulting product may be contaminated. For example, the meat of hundreds of animals may be present in a single hamburger patty; this compounds the danger of contracting food poisoning.

Another source of risk is the water used to clean fruits and vegetables. Washing uncooked produce is an important step to ensuring safety, but the danger is not eliminated. Unclean water for washing or chilling fruits and vegetables elevates the risk that the food will be contaminated. This is coupled with the risk posed by pesticides remaining on the food. Finally, special care must be taken when consuming mushrooms; some varieties are quite poisonous and a mistake can have serious consequences.