Foodborne Illness

More than 250 known foodborne diseases are caused by bacteria, viruses or parasites. Some are caused by toxins, or poisons, from bacteria; others are caused by the human body's reactions to the microbe itself. The most common cause is harmful bacteria.

Most foods contain small quantities of bacteria. Each day we are exposed to thousands of bacteria, but most don’t cause disease. For example, the bacteria used to make cheese and yogurt are safe and even healthy. Bacteria are normal, and usually harmless, inhabitants of skin and mucus membranes of the body, including the digestive tract. Some bacteria, however, create problems for our digestive system. Foodborne illness develops when certain harmful bacteria such as Salmonella, Shigella or Escherichia coli (E. coli) O157:H7, or large numbers of normally harmless bacteria, get into the body from food and multiply in the intestinal tract.

A century ago, typhoid fever, tuberculosis and cholera were common foodborne diseases. Because of improvements such as pasteurization of milk, safe canning and disinfection of water supplies these diseases are no longer common in the United States. New causes, however, continue to appear. For example, in 1998, a new strain of the bacterium Vibrio parahemolyticus contaminated oyster beds in Galveston Bay and caused an epidemic of diarrheal illness in people who ate the oysters raw.

Some bacteria may be present on foods when you purchase them; contamination can also occur when they are prepared for cooking. Raw meat and poultry may become contaminated during slaughter. Seafood may become contaminated during harvest or through processing. Eggshells and, rarely, the egg itself may be contaminated with Salmonella. Produce such as lettuce, tomatoes, sprouts and melons can become contaminated during growing, harvesting, processing, storing, shipping or final preparation.

Cooked food that has been left at room temperature for two or more hours can be contaminated by new bacteria. Freezing food slows or stops bacterial growth but does not kill bacteria. Once the food is thawed, bacteria begin to grow. Refrigeration slows the growth of some bacteria. Only thorough cooking kills bacteria.

The most common bacteria that cause foodborne infections are Campylobacter, Salmonella and E. coli O157:H7 and a group of viruses called caliciviruses, also known as the Norwalk and Norwalk-like viruses. Other organisms that can be transmitted by food or drink are Shigella, hepatitis A and the parasites Giardia lamblia and Cryptosporidia. Bacteria that produce toxins include Staphylococcus aureus, which can cause intense vomiting, and Clostridium botulinum, which can cause paralysis and death . Even if these bacteria are killed, the toxin they have produced is not destroyed and will cause illness. Food or drink can also carry disease-causing parasites such as Entamoeba histolyticaor Cyclospora, which was identified as a cause of diarrheal illness related to Guatemalan raspberries in 1996.  

Most cases of foodborne illness in healthy adults cause no long-term effects.

Causes of Contamination

Foodborne illness is caused when food is handled or cooked improperly, or stored inadequately then eaten. Even if a food is properly handled and safely cooked and stored, it can be contaminated when it is exposed to bacteria from other sources. These sources include raw products and meat juices, as well as food handlers who may have harmful bacteria on their hands. In September 2006, E. coli contaminated fresh spinach. More than 120 people in more than 20 states were hospitalized and at least two people died.

Symptoms

Symptoms of foodborne illness vary depending on the type of bacterium, virus or parasite that has contaminated the food. Common symptoms include diarrhea, gas pains, abdominal cramps, nausea and vomiting, and fever or chills. Because these symptoms can resemble the flu, people often do not know that they have a foodborne illness. Some symptoms, such as double vision, droopy eyelids, or difficulty speaking, swallowing or breathing, point to a much more serious foodborne illness called botulism. If you have any of these symptoms, you should see your doctor right away.

Some people may become ill after ingesting only a few harmful bacteria, while others can ingest thousands of bacteria and have no symptoms at all. In a few types of foodborne illness, symptoms appear as early as a half hour after eating the contaminated food. But symptoms from most causes do not develop for several days or weeks. Symptoms from most infections usually last only a day or two, but can last a week to 10 days. For most healthy people, these illnesses are not long-lasting or life-threatening. They can be severe in the very young, the very old, and in people with certain diseases and conditions. People at greatest risk of having foodborne illness are those with weaker immune systems. These include very young children, pregnant women, people with chronic diseases such as AIDS or diabetes, people with stomach problems and elderly adults. People who take medications that reduce stomach acid, which normally helps destroy bacteria, or oral steroids, which are sometimes used to treat asthma, arthritis and liver disease, also are at risk.

Treatment

Most mild symptoms of foodborne illness go away on their own without medications. They can last anywhere from 24 hours to several days, however. In some cases, foodborne illness can be dangerous because the accompanying vomiting and diarrhea can cause severe dehydration. If the infection spreads from the intestines to the bloodstream, antibiotics may be prescribed.

Botulism, one of the most serious types of foodborne illness, requires immediate medical attention. If left untreated, botulism can cause death.

Self-Care Steps for Foodborne Illness

• Rest and drink plenty of fluids. Avoid alcohol, caffeine and milk products. Use oral electrolyte solutions to replace fluid losses, but avoid sports drinks because they don’t contain the proper balance of electrolytes.

• When you begin to have an appetite, try eating semi-solid and low-fiber foods, such as soda crackers and toast.

• See your doctor if your symptoms last longer than a few weeks or if you develop severe diarrhea with decreased urination, bloody stools, fever, abdominal pain, cramps or yellow skin and yellow eyes (jaundice).

• It’s OK to take antidiarrheal medicines as long as you don't have a high fever or blood in your stool. Bismuth sulfate (Pepto-Bismol) may shorten the course of illness and Immodium is safe for adults.

• Call the local health department if the suspect food was served at a large gathering, if it was from a restaurant or other food service facility, or if you bought the product at a store.

Prevention

Bacteria multiply rapidly between 40 and 140 degrees F. To keep food from entering this danger zone, follow these guidelines:

• Store food in the refrigerator or freezer.

• Cook foods of animal origin well:

  • Cook ground beef, pork, veal and lamb to 160 degrees F; ground chicken or turkey to 165 degrees F.

  • Cook fresh beef, veal, lamb beef, pork, veal and lamb to at least 145 degrees F for rare and 170 degrees F for well done.

  • Cook poultry to 170 to 180 degrees F.

  • Cook fresh pork to 160 degrees F for medium and 170 degrees F for well done.

  • Cook egg dishes until yolk and white are firm.

• Maintain hot, cooked food at 140 degrees F or above.

• When reheating cooked food, reheat to 165 degrees F.