What is Foodborne Illness? Symptoms, Causes, Treatments

Foodborne illness is an infection or irritation of the gastrointestinal (GI) tract caused by food or beverages that contain harmful bacteria, parasites, viruses, or chemicals. Common foodborne illness symptoms include vomiting, diarrhea, abdominal pain, fever, and chills.

Most foodborne illnesses are acute, meaning they happen suddenly and last a short time, and most people recover on their own without treatment. Occasionally, foodborne illness may lead to more serious complications. Each year, an estimated 48 million people in the United States experience a foodborne illness. Foodborne illnesses cause 128, 000 hospitalizations and about 3,000 deaths in the United States annually.

What are the symptoms of foodborne illness?

What are the symptoms of foodborne illness?

Some symptoms of foodborne illness are dependent on the type of microorganism present. However, many foodborne illnesses share common symptoms including:
• Vomiting
• Diarrhea or bloody diarrhea
• Abdominal pain
• Fever
• Chills
Symptoms can range from mild to serious and can last from a few hours to several days.

In addition, the toxins produced by C. botulinum and some chemicals affect the nervous system, causing symptoms such as
• headache
• tingling or numbness of the skin
• blurred vision
• weakness
• dizziness
• paralysis

What causes foodborne illness?

What causes foodborne illness?

The majority of foodborne illness is caused by certain strains of bacteria and viruses. Parasites and chemicals may also cause foodborne illness.


Harmful bacteria may already be present in foods when they are purchased. Raw foods including meat, poultry, fish and shellfish, eggs, unpasteurized milk and dairy products, and fresh produce often contain bacteria that cause foodborne illness. This contamination can occur at any time during growth, harvesting or slaughter, processing, storage, and shipping of food.

Foods may also be contaminated with bacteria during food preparation in a restaurant or home kitchen. If hands, kitchen utensils, cutting boards, and other kitchen surfaces that come into contact with raw food are not washed, cross-contamination may occur.

When food is stored incorrectly, it gives bacteria the opportunity to multiply; room temperature (between 40 and 140F) is an ideal condition for bacteria to grow. Refrigerated food items should be kept at 40F or below, while hot foods should be kept at 140F or above. Refrigeration can prevent bacteria from growing, and freezing food can further slow or even stop this growth. However, bacteria in refrigerated or frozen foods become active again when food is brought to room temperature, so these foods should be thoroughly cooked to kill any harmful bacteria.

More About Bacteria


Viruses that cause foodborne illness can be spread by the stool and vomit of those already infected. Infected persons may contaminate food and drinks if proper hygiene is not adhered to during food preparation. Viruses can also be spread through the use and/or ingestion of contaminated water or by ingestion of fish or shellfish grown in contaminated water.

More About Viruses


Parasites are spread through water that has been contaminated with the stools of infected animals or humans. Infected persons may contaminate food and drinks if proper hygiene is not adhered to during food preparation. Additionally, foods that come into contact with contaminated water during growth or preparation can become contaminated with these parasites.

More About Parasites


Fish or shellfish may feed on algae that produce toxins, leading to high concentrations of these toxins in their flesh. Some types of fish may be contaminated with bacteria that produce toxins if they are not properly refrigerated before they are cooked or served. Certain types of wild mushrooms also contain poisonous compounds. In addition, unwashed fruits and vegetables can contain high concentrations of pesticides.

Who can get a foodborne illness?

Who can get foodborne illness?

Anyone can get a foodborne illness. However, some people are more likely to develop foodborne illnesses than others, including infants and children, pregnant women and their unborn children, older adults, and people with compromised immune systems. These groups also have a greater risk of developing severe symptoms or complications from foodborne illnesses.

What are the complications of foodborne illness?

What are the complications of foodborne illness?

Foodborne illnesses can cause dehydration, hemolytic uremic syndrome (HUS), and other complications. Acute foodborne illnesses may also lead to chronic health problems or even death.


When someone does not drink enough fluids to replace those that are lost through vomiting and diarrhea, dehydration can result. Severe dehydration may require intravenous fluids and hospitalization. Untreated severe dehydration can cause serious health problems such as organ damage, shock, or coma. Infants, children, older adults, and people with weak immune systems have the greatest risk of becoming dehydrated.

Signs of dehydration include:

  • Excessive thirst
  • Infrequent urination
  • Dark-colored urine
  • Lethargy, dizziness, or faintness
  • Dry mouth and tongue
  • Lack of tears when crying
  • No wet diapers for 3 hours or more
  • High fever
  • Unusually cranky or drowsy behavior
  • Sunken eyes, cheeks, or soft spot in the skull


Hemolytic uremic syndrome (or HUS) is a rare disease that primarily affects children younger than 10. HUS develops when E. coli bacteria lodged in the digestive tract make toxins that enter the bloodstream. The toxins start to destroy blood cells that aid in clotting and the lining of the blood vessels. Symptoms of HUS (including irritability, paleness, and decreased urination) may develop up to a week after E. coli symptoms appear. HUS may lead to acute renal failure and negatively affect other organs and the central nervous system.

In the United States, E. coli O157:H7 infection is the most common cause of HUS, with a recent study showing that about 6 percent of people with E. coli O157:H7 infections develop it. Infection with other strains of E. coli, other bacteria, and viruses may also cause HUS. Children younger than age 5 are most at risk for developing HUS, but females and people age 60 and older also have an increased risk.

Most people who develop HUS recover with treatment. Research shows that in the United States between 2000 and 2006, fewer than 5 percent of people who developed HUS died of the disorder, with older adults having the highest mortality rate.* However, some who recover from HUS earlier in life develop chronic complications, including kidney problems, high blood pressure, and diabetes.

Other Complications

  • Paralysis of the muscles that control breathing from the toxin produced by Clostridium botulinum and certain chemicals in fish and seafood.
  • Spontaneous abortion or stillbirth in pregnant women caused by Listeria monocytogenes infections.
  • Chronic disorders, including Reactive Arthritis from Campylobacter jejuni and Salmonella infections, Irritable Bowel Syndrome (IBS), and Guillain-Barré Syndrome, a disorder characterized by muscle weakness or paralysis,thought to occur after foodborne illnesses caused by bacteria, most commonly Campylobacter jejuni (C.jejuni) .
  • Possible increased risks of high blood pressure, kidney problems, and cardiovascular disease from E. Coli O157:H7 infections.

When should people with foodborne illness see a health care provider?

When should people with foodborne illness see a health care provider?

People with any of the following symptoms should see a health care provider immediately:

  • Signs of dehydration
  • Prolonged vomiting that prevents keeping liquids down
  • Diarrhea for more than 2 days in adults or for more than 24 hours in children
  • Severe pain in the abdomen or rectum
  • Fever higher than 101 degrees F
  • Stools containing blood or pus
  • Stools that are black and tarry
  • Signs of nervous system failure
  • Signs of HUS

How is foodborne illness diagnosed?

How is foodborne illness diagnosed?

Health care providers may ask about symptoms, foods and beverages recently consumed, and medical history and also perform a physical examination in order to diagnose a foodborne illness.

In addition, diagnostic tests including a stool culture or a culture of a sample of vomit or suspected food (if available) may be performed. A health care provider may perform additional medical tests to rule out diseases and disorders that cause symptoms similar to those of foodborne illnesses.

How is foodborne illness treated?

How is foodborne illness treated?

The most common treatment for mild cases of foodborne illness is replacing lost fluids and electrolytes to prevent dehydration. Over-the-counter medications may help stop diarrhea in adults, however, these medications should not be used by people with bloody diarrhea, as this may be a sign of bacterial or parasitic infection. If diarrhea is caused by bacteria or parasites, over-the-counter medications may prolong the problem. Medications to treat diarrhea in adults can be dangerous for infants and children and should only be given with a health care provider’s guidance. If the specific cause of the foodborne illness is diagnosed, a health care provider may prescribe medications, such as antibiotics, to treat the illness. Hospitalization may be required to treat more severe cases of foodborne illness.

What dietary recommendations are given for those suffering from foodborne illness?

What dietary recommendations are given for those suffering from foodborne illness?

  • Drinking plenty of liquids such as fruit juices, sports drinks, caffeine-free soft drinks, and broths to replace fluids and electrolytes.
  • Sipping small amounts of clear liquids or sucking on ice chips if vomiting is still a problem.
  • Gradually reintroducing food, starting with bland, easy-to-digest foods such as rice, potatoes, toast or bread, cereal, lean meat, applesauce, and bananas.
  • Older adults and adults with weak immune systems should also drink oral rehydration solutions to prevent dehydration.
  • Avoiding fatty foods, sugary foods, dairy products, caffeine, and alcohol until recovery is complete.

Infants and children present special concerns, as they are likely to become dehydrated more quickly from diarrhea and vomiting because of their smaller body size. The following steps may help relieve symptoms and prevent dehydration in infants and children:

  • Giving oral rehydration solutions to prevent dehydration.
  • Giving bland food as soon as the child is hungry.
  • Giving infants breast milk or full strength formula, along with oral rehydration solutions.

How are foodborne illnesses prevented?

How are foodborne illnesses prevented?

Foodborne illnesses can be prevented by properly storing, cooking, cleaning, and handling foods:

  • Hands should be washed at least 20 seconds with warm, soapy water before and after handling raw meat, poultry, fish, shellfish, produce, or eggs, as well as after using the bathroom, changing diapers, or touching animals.
  • Raw and cooked perishable foods should be refrigerated or frozen promptly. Refrigerated food should be stored at 40F or lower and frozen food should be stored at minimum 0F. Frozen food should be thawed in the refrigerator or in the microwave followed by immediate cooking.
  • A meat thermometer should be used to ensure foods are cooked to the appropriate internal temperature. Click here for a chart of internal cooking temperatures for food.
  • Fruits and vegetables should be washed under running water just before eating, cutting, or cooking. A produce brush can be used under running water to clean fruits and vegetables with firm skin.
  • Raw meat, poultry, seafood, and their juices should be kept away from other foods.
  • Utensils and surfaces should be washed with hot, soapy water before and after they are used to prepare food. Diluted bleach—1 teaspoon of bleach to 1 quart of hot water—can also be used to sanitize utensils and surfaces.

*Gould HL, Demma L, Jones TF, et. al. Hemolytic uremic syndrome and death in persons with Escherichia coli O157:H7 infection, Foodborne Diseases Active Surveillance Network sites, 2000–2006. Clinical Infectious Diseases. 2009:49(10):1480–1485.

More information about preventing foodborne illness: www.foodsafety.gov

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