Cause

Food poisoning is an illness caused by eating or drinking contaminated food. For example, you can get food poisoning by eating food contaminated by harmful organisms, such as bacteria, parasites, and viruses.

The most common ways that harmful organisms are spread are:

• During food processing. It is normal to find bacteria in the intestines of healthy animals that we use for food. If bacteria come in contact with meat or poultry during processing, they can contaminate the food. Campylobacter, salmonella, and E. coli are often spread in this way. In one test, the U.S. Centers for Disease Control and Prevention (CDC) found that campylobacter was present in almost half of the raw chicken breasts tested.¹
• During food growing. Fresh fruits and vegetables can be contaminated if they are washed or irrigated with water that is contaminated with animal manure or human sewage. Staph food poisoning, E. coli, and shigellosis are often spread through contaminated water.
• During food handling. Food can be contaminated when an infected person handles the food or if it comes in contact with another contaminated product. For example, if you use the same cutting board for both chopping vegetables and preparing raw meat, you risk contaminating the vegetables.
• Through the environment. Many harmful organisms that are commonly found in dirt, dust, and water can find their way into the foods we eat. These organisms include Clostridium botulinum, Clostridium perfringens, and Cryptosporidium parvum. Environmental conditions—such as water polluted by farm runoff—may make this type of infection more frequent.

Follow the links below for more information, including how specific organisms are spread:

• Botulism (Clostridium botulinum)
• Campylobacteriosis (Campylobacter)
• C. perfringens food poisoning (Clostridium perfringens)
• Hepatitis A
• Listeriosis (Listeria monocytogenes)
• Marine toxins
• Noroviruses
• Salmonellosis (Salmonella typhimurium, Salmonella enteritidis)
• Shigellosis (Shigella)
• Staph food poisoning (Staphylococcus aureus)
• Toxoplasmosis (Toxoplasma gondii)
• Vibrio vulnificus food poisoning

Toxoplasmosis and listeriosis are dangerous to a pregnant woman and her fetus. For more information on toxoplasmosis, see the topic Toxoplasmosis During Pregnancy.

For information on E. coli O157:H7, see the topic E. Coli Infection. Other types of E. coli infection (enterotoxigenic E. coli) are frequent in the developing world and are a major cause of traveler's diarrhea.