Foodborne illness, commonly called food poisoning, occurs when someone eats or drinks something contaminated with harmful bacteria, viruses, parasites, chemicals, or natural toxins. Foodborne illnesses can range from mild stomach upset to serious illnesses requiring medical care.

Food contamination can happen at any point during the food process — from growing and harvesting, to processing and preparation, to storage and handling in your own kitchen. Following safe food handling practices can help reduce the risk of foodborne illness.

What Causes Foodborne Illness?

Foodborne illnesses are most often caused by:

Bacteria

Bacteria are one of the most common causes of food poisoning. Some bacteria can grow in food and produce toxins that make people sick.

Examples include:

• Salmonella — often associated with raw or undercooked eggs, poultry, meat, and contaminated produce.

• Escherichia coli (E. coli) — can be found in undercooked ground beef, raw produce, and unpasteurized products.

• Listeria — can grow even in refrigerated foods and is commonly associated with deli meats, soft cheeses, and unpasteurized foods.

• Campylobacter — often linked to raw poultry, unpasteurized milk, and contaminated water.

Viruses

Viruses can spread through contaminated food, water, or contact with an infected person.

• Norovirus is one of the leading causes of foodborne illness and can spread easily through contaminated food, surfaces, and poor hand hygiene.

Parasites

Some parasites can contaminate food and water and cause illness.

Examples include:

• Cyclospora

• Toxoplasma

Chemicals and Natural Toxins

Food poisoning can also occur when foods contain harmful chemicals or naturally occurring toxins.

Examples include:

• Improperly prepared wild mushrooms

• Certain fish toxins

• Food contaminated with chemicals

• Toxins produced by certain bacteria