"Food poisoning” or foodborne disease sickens an estimated 76 million people each year in the United States. That means nearly one in every four people is sickened each year by exposure to through contaminated food or drink. But what are the most common causes of foodborne diseases?

Many cases of food poisoning are actually caused by infectious organisms. There are actually around 250 disease causing organisms that can sicken people when they are consumed. Foodborne disease can be caused by bacteria, viruses, or parasites. Some diseases are caused by toxins from disease-causing microbes while others are caused by the human body’s reactions to the microbe itself. Other diseases are true poisonings, caused by harmful toxins or chemicals that have contaminated the food, such as poisonous mushrooms.

While there are several possible causes of foodborne illness, four microbes are responsible for the majority of all foodborne illness in the United States. Worldwide, typhoid fever, tuberculosis, and cholera are still common foodborne diseases, but improvements in food safety and vaccination have virtually eradicated these diseases in the United States.

The 4 most common causes of foodborne illness in the United States are:

• Campylobacter. This bacterium causes fever, diarrhea, and abdominal cramps and according to the Centers for Disease Control and Prevention (CDC), is the most commonly identified bacterial cause of diarrheal illness in the world. Campylobacter bacteria live in the intestines of birds and most raw poultry harbors the bacteria. Eating undercooked chicken or food that has been contaminated with raw chicken juice is the most frequent source of Campylobacter infection. 


• Salmonella. This bacterium is also widespread in the intestines of birds, along with reptiles and mammals. It can spread to humans via a variety of foods of animal origin, but raw or undercooked chicken is a major source of infection. Like Campylobacter, Salmonella also tends to cause fever, diarrhea, and abdominal cramps, but in people with underlying health problems or weakened immune systems it can invade the bloodstream (bacteremia) and become life threatening. 


• E. coli. E coli is a bacterium that lives in the intestines of cattle and other similar animals, including humans. There are many strains of E. coli bacteria but only certain types cause illness. The strain that is responsible for most cases of foodborne illness in people is called E. coli O157:H7. In humans, exposure usually occurs through consumption of food or water that has been contaminated with microscopic amounts of cow feces. The illness that occurs is often a severe and bloody diarrhea and painful abdominal cramps, without a fever (or with a very low-grade fever). In up to 5 percent of cases, a complication called hemolytic uremic syndrome (HUS) develops several weeks after the initial symptoms.  HUS causes temporary anemia, profuse bleeding, and kidney failure and may lead to death.


• Norovirus. Also known as calicivirus, Norwalk virus, or Norwalk-like virus, norovirus is an extremely common cause of foodborne illness. However, due to the lack of a widely-available diagnostic test, the disease is often suspected but rarely diagnosed. It causes an acute gastrointestinal illness, usually with more vomiting than diarrhea, which tends to resolve within two days. Unlike the other foodborne pathogens listed above, it is believed that norovirus spreads primarily from one infected person to another via food they have touched, instead of through animals. Infected kitchen workers can contaminate a salad or sandwich as they prepare it, if they have the virus on their hands. Thus, large outbreaks of norovirus are common in places with central eating locations such as cruise ships, schools, and even hospitals.

For more information about foodborne illness, see the UDSA’s Food Safety Information Center or the CDC’s Food Safety Office. If you have questions about foodborne illness, ask the people in the Healia Health Community for E. Coli Infections or the Healia Health Community for Salmonella Infections, or ask an expert at Healia Health Communities.


_{Source: CDC – Foodborne illness, Jan 2005. http://www.cdc.gov/ncidod/dbmd/diseaseinfo/foodborneinfections_g.htm#mostcommon}

_{Photo: [n], Flickr, Creative Commons}