Causes and Symptoms

Symptoms Graphic

Foodborne illness results from consuming foods contaminated with bacteria, viruses, parasites, toxins or chemicals. Most cause acute illness and involve diarrhea, nausea and vomiting – but foodborne illness can also cause long-term health outcomes.

There are more than 250 known foodborne diseases. In addition to the causes listed above, many chemicals such as pesticides, and toxins produced by bacteria and fungi, can also cause foodborne illness. For example, staphylococcal aureus (staph) is a bacterium that produces toxins that can make people ill.

Infectious foodborne pathogens – those caused by bacteria or viruses – are often linked to animal sources. For example, chickens often have Salmonella in their intestines, which can contaminate raw chicken meat and eggs. Manufacturing and agricultural practices such as spreading manure and irrigating crops can also spread foodborne pathogens and contaminate fruits and vegetables. In addition to contaminated foods, it is also possible to acquire foodborne illness through direct contact with animals like chickens, cows, goats, and pets including dogs and reptiles. Good handwashing should be practiced after interacting with all animals and prior to handling or preparing food. Some foodborne illnesses, such as norovirus and rotavirus, can spread from person to person. People who exhibit symptoms of foodborne illness should avoid handling food.

Common symptoms of foodborne illness are diarrhea (including bloody diarrhea), nausea, vomiting, and abdominal cramps. While affected individuals often assume the last thing they ate caused their illness, this is typically not the case. Symptoms commonly begin 12-72 hours after consuming a contaminated food. This is called the “incubation period.” Incubation periods for common foodborne pathogens are listed below.


Incubation Time


12-48 hours


21-72 hours

Clostridium perfringens

6-24 hours


2-5 days

Staphylococcus aureus

0.5-8 hours

E. coli

3-4 days

Listeria monocytogenes

1-4 weeks


Within 24 hours

For most relatively healthy people, foodborne illness symptoms will only last a few days. However, foodborne pathogens can also cause long-term (or chronic) health outcomes. These long-term health outcomes may range from gastrointestinal disorders such as irritable bowel syndrome to immune disorders including reactive arthritis and Guillain-Barré syndrome. Among individuals who develop hemolytic uremic syndrome (HUS) following infections with Shiga toxin-producing E. coli, kidney failure and hypertension are common and many individuals require dialysis and transplants in the years following their illness. To learn more about the long-term health outcomes associated with foodborne illness, visit our research page or read our 2009 white paper.

To learn more about the causes and symptoms of foodborne illness, see CDC’s A-Z Index for Foodborne Illness.


CDC Guide on Food and Water Safety for Travelers

CDC Guide on Foodborne Illness and Germs

CDC Guide on Foods Most Likely to Cause Food Poisoning

CDC A-Z Index for Foodborne Illness