How are foodborne illnesses spread?

An estimated 55% of foodborne illnesses are caused by improper cooking and storage of foods. Fully 24% result from negligent hygiene by food handlers, especially the failure to wash hands before handling food. About 3% of food poisoning cases are from an unsafe food source.

Most foodborne illnesses, both viruses and bacteria, are spread by bodily fluids or particles of soil or animal or human excrement. Animal and poultry carcasses in meat-packing plants may have dirt or excrement still clinging to them. Vegetables may come into contact with animal manure as fertilizer, or in the course of harvesting and transport.

Processing plants that fail to follow industry standards for safe handling of foods can allow dangerous bacteria to multiply in their products. The widespread recall of salmonella-contaminated peanut butter and other peanut products in January 2009 resulted from manufacturers’ failure to follow fundamental hygiene procedures. State health inspectors found bird feathers, rodent droppings, dead rodents, cockroaches, mold, and a leaking roof at the two plants responsible for the contaminated products.

In many large scale outbreaks of food poisoning involving multiple sources of the suspect food, as from several processing plants or a large number of farms, it has often been impossible to isolate the source of contamination. The US Department of Agriculture and the Food and Drug Administration strongly urge that all farms and processing plants follow industry standard procedures for cleanliness and safety.

Even when food arrives in stores, restaurants and institutional kitchens, infected particles may still be found on it. Infection may also be carried by food handlers in any of these settings. It is critically important that all the people who handle, prepare, and serve food practice the following food safety procedures:

• Everyone involved in food preparation and food service should wash both hands thoroughly, including under the fingernails, before working with food.
• If a worker shifts from one type of food to another, e.g. raw to cooked, or poultry to vegetables, he or she should wash both hands before moving to the new food.
• Wash pots, pans, trays, knives, cooking utensils, preparation surfaces, and anything else that touches food as carefully as you wash your hands.
• If a food handler has cuts on the hands or wrists, or a nose or eye infection, that person should not handle food until the condition has resolved.
• If food is to be stored longer than two hours, cold foods should be stored at temperatures lower than 40°, and hot foods should be maintained at 140° higher.
• Cooked food should be stored in wide, shallow containers and refrigerated as soon as possible.