Contamination Contributing Factors

Background

Technical definitions for the 30 contributing factors for foodborne illness outbreaks are organized around the three types of contributing factors (contamination, proliferation, and survival). Staff from CDC, the Food and Drug Administration (FDA), and state health departments helped revise these contributing factors to show how foodborne illness outbreaks evolve.

Definitions

Contamination contributing factors introduce or otherwise permit contamination. These factors relate to how the etiologic agent got onto or into the food.

C1 Toxin or chemical agent naturally part of tissue in food

A natural toxin found in a plant, fungus, or animal; OR a chemical agent of biologic origin that occurs naturally in the plant, fungus, or animal or bioaccumulates in the plant, fungus, or animal before or soon after harvest or slaughter. Examples of this type of contributing factor include:

• Ciguatera fish poisoning due to consumption of tropical marine finfish which have bioaccumulated naturally occurring ciguatera toxins through their diet.
• Scombroid fish poisoning due to consumption of fish containing elevated levels of histamine.
• Mushroom poisoning due to consumption of toxic mushrooms.

C2 Poisonous substance or infectious agent intentionally added to food to cause illness (does not include injury)

A poisonous substance, chemical agent, or infectious agent was intentionally/deliberately added to the food in quantities sufficient to cause illness. Poisons added because of sabotage, mischievous acts, and attempts to cause panic or for blackmail fall into this category. This CF does not apply to physical objects (such as a sharp object) intentionally added to food to cause injury. Examples of this type of contributing factor include:

• Cyanide or phenolphthalein deliberately added to food to cause illness
• Methomyl pesticide intentionally added to food to cause illness
• Salmonella intentionally added to food to cause illness.

C3 Poisonous substance accidentally/inadvertently added to food

A poisonous substance or chemical agent was accidentally or inadvertently added to the food. This addition typically occurs at the time of preparation or packaging of the food. Misreading labels, resulting in either mistaking poisonous substances for foods or incorporating them into food mixtures, would also fall into this category. Examples of this type of contributing factor include:

• Sanitizer or cleaning compound accidentally added to food or metallic ingredient accidentally added to food (e.g., copper in cake icing).

C4 Ingredients toxic in large amounts accidentally added to food

An approved ingredient was accidentally added in excessive quantities to the food so as to make the food unacceptable for consumption. Examples of this type of contributing factor include:

• Excessive amount of niacin in bread.
• Excessive amount of nitrites in cured meat.
• Excessive amount of ginger powder in gingersnaps.

C5 Container or equipment used to hold or convey food was made with toxic substances

The container that held or conveyed the implicated food is made of toxic substances. The toxic substance either migrates into the food or leaches into the food through contact with highly acidic foods. Examples of this type of contributing factor include:

• Galvanized container used to store acidic food/beverage.
• Flour stored in a container that previously held toxic materials.
• Pre-made ice stored in a toxic container.

C6 Food contaminated by animal or environmental source at point of final preparation/sale

The food was contaminated at point of final preparation/sale (e.g., restaurant, private home, etc.) by animal or environmental source(s), such as from dripping, flooding, airborne contamination, access of insects or rodents, and other situations conducive to contamination. Examples of this type of contributing factor include:

• Mouse feces in pantry contaminates food.
• A leaky roof permits water to seep into a walk-in refrigerator and contaminates stored food.

C7 Food contaminated by animal or environmental source before arriving at point of final preparation (pre- or post-harvest)

The food was contaminated before arriving at the point of final preparation by animal or environmental sources, either pre-harvest (e.g., growing field, harvest area, irrigation water, etc.) or post-harvest (e.g., processing or distribution facility, in warehouse storage, during transit, etc.).

Note: Traceback may implicate the identification of where the food was contaminated (pre-harvest versus post-harvest). If identified, please indicate this in the Point of Contamination question in the NORS interface; otherwise, please select "before point of final/preparation/sale: unknown."

Pre-harvest examples of this type of contributing factor include:

• Shellfish from sewage polluted waters or closed beds.
• Crops watered by contaminated irrigation water.
• Produce grown in soil contaminated by geese.
• Live poultry contaminated with Campylobacter then slaughtered and poultry distributed to retailers.
• Eggs contaminated with Salmonella.

Post-harvest examples of this type of contributing factor include:

• Peanut butter contaminated by bird droppings in a processing plant.
• Cheese contaminated with Listeria in a cheese manufacturer plant.

C8 Cross-contamination of foods, excluding infectious food workers/handlers

The pathogen was transferred to the food source from contaminated surfaces, foods, and/or fomites to include, but not limited to, food worker's hands, cutting boards, preparation tables, utensils, processing lines, etc. Examples of this type of contributing factor include:

• A ready-to-eat (RTE) food was prepared on the same cutting board as contaminated raw poultry.
• A food worker handled contaminated raw foods without subsequently washing their hands, and afterward handled an RTE food.
• Materials used to clean equipment (e.g., cloths, sponges, etc.) that processed contaminated raw foods were subsequently used on surfaces that came in contact with RTE foods without first being disinfected.
• Contaminated raw foods touched or dripped onto foods that were not subsequently cooked.
• Contaminated raw foods were processed on shared lines with non-contaminated food items.

C9 Contamination from infectious food worker/handler through bare hand contact with food

A food worker/handler, who is suspected or confirmed to be infectious, used their bare hands to touch/prepare foods that are not subsequently cooked. If it is unknown whether the food worker was wearing gloves or not, then cite C11. If there is evidence for both bare hand contact and glove-hand contact with the food, both C9 and C10 should be cited.

This is a typical situation that precedes outbreaks caused by norovirus or staphylococcal enterotoxins.

Potential reasons to suspect or confirm that a food worker is "infectious"—an all-inclusive term used to describe all persons who are colonized by, infected with, a carrier of, or ill due to a pathogen:

1. They recently displayed or admitted to common enteric disease symptoms (e.g., diarrhea, vomiting, nausea, fever) that may be similar to symptoms identified in those who are ill in the outbreak investigation.
2. Their household member exhibited similar symptoms directly preceding the outbreak.
3. They tested positive for an enteric pathogen.
4. Other epidemiologic or environmental evidence.

Examples of this type of contributing factor include:

• An infectious food worker/handler preparing deli meat without wearing gloves contaminated the food served to restaurant patrons.

C10 Contamination from infectious food worker/handler through glove-hand contact with food

A food worker/handler, who is suspected or confirmed to be infectious, used their glove-hands to touch/prepare foods that were not subsequently cooked. If it is unknown whether the food worker was wearing gloves or not, then cite C11. If there is evidence for both bare hand contact and glove-hand contact with the food, both C9 and C10 should be cited.

This is a typical situation that precedes outbreaks caused by norovirus or staphylococcal enterotoxins.

See C9 for a further description of reasons to suspect or confirm an infectious food worker/handler.

Examples of this type of contributing factor include:

• An infectious food worker/handler prepared deli meat while wearing gloves that were not changed after coughing into their hand, which contaminated the food served to restaurant patrons.

C11 Contamination from infectious food worker/handler through unknown type of hand contact with food or indirect contact with food

A food worker/handler, who is suspected or confirmed to be infectious, used their hands to touch/prepare foods that were not subsequently cooked, but the epidemiologic/environmental investigation was unable to determine whether or not the food worker was wearing gloves during food preparation OR a food worker/handler, who is suspected or confirmed to be infectious, contaminated the food indirectly (no direct bare-hand or glove-hand contact with the food).

This is a typical situation that precedes outbreaks caused by norovirus or staphylococcal enterotoxins.

See C9 for a further description of reasons to suspect an infectious food worker/handler.

Examples of this type of contributing factor include:

• An infectious food worker/handler prepared deli meat, though it was unknown if gloves were worn, contaminated the food served to restaurant patrons.
• An infectious food worker/handler contaminated utensils that subsequently contaminated food served to restaurant patrons.

C12 Contamination from infectious non-food worker/handler through direct or indirect contact with food

A person other than a food handler/worker who is suspected or confirmed to be infectious, contaminated ready-to-eat foods that were later consumed by other persons, resulting in spread of the illness. A "non-food handler/worker" is considered to be any person who is not directly involved in the handling or preparation of the food before service.

Potential reasons to suspect or confirm that a non-food worker is "infectious"—an all-inclusive term used to describe all persons who are colonized by, infected with, a carrier of, or ill due to a pathogen:

1. They recently displayed or admitted to common enteric disease symptoms (e.g., diarrhea, vomiting, nausea, fever, etc.) that may be similar to symptoms identified in those who are ill in the outbreak investigation.
2. Their household member exhibited similar symptoms directly preceding the outbreak.
3. They tested positive for an enteric pathogen.
4. Other epidemiologic or environmental evidence.

Examples of this type of contributing factor include:

• An ill person attended an event and contaminated ready-to eat-foods in a buffet line by handling food before someone else consumed it.
• Pizza was prepared by a healthy food worker and arrived pathogen-free. An ill non-food worker, such as a mother, rearranged pizza slices onto plates before serving the slices to a group of children at a birthday party, and these children subsequently developed foodborne illness.
• An infectious non-food worker/handler contaminated utensils that subsequently contaminated food at a potluck.

C13 Other source of contamination (specify)

A form of contamination that does not fit into the above categories; the factor should be specified in the “Contributing Factors Comments” section.