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Foodborne illnesses are infections or irritations of the gastrointestinal (GI) tract caused by food or beverages that contain harmful bacteria, parasites, viruses, or chemicals. The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. Common symptoms of foodborne illnesses 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. Rarely, foodborne illnesses may lead to more serious complications. Each year, an estimated 48 million people in the United States experience a foodborne illness. Foodborne illnesses cause about 3,000 deaths in the United States annually.1
The majority of foodborne illnesses are caused by harmful bacteria and viruses.2 Some parasites and chemicals also cause foodborne illnesses.
Bacteria are tiny organisms that can cause infections of the GI tract. Not all bacteria are harmful to humans.
Some 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 illnesses. Bacteria can contaminate food—making it harmful to eat—at any time during growth, harvesting or slaughter, processing, storage, and shipping.
Foods may also be contaminated with bacteria during food preparation in a restaurant or home kitchen. If food preparers do not thoroughly wash their hands, kitchen utensils, cutting boards, and other kitchen surfaces that come into contact with raw foods, cross-contamination—the spread of bacteria from contaminated food to uncontaminated food—may occur.
If hot food is not kept hot enough or cold food is not kept cold enough, bacteria may multiply. Bacteria multiply quickly when the temperature of food is between 40 and 140 degrees. Cold food should be kept below 40 degrees and hot food should be kept above 140 degrees. Bacteria multiply more slowly when food is refrigerated, and freezing food can further slow or even stop the spread of bacteria. However, bacteria in refrigerated or frozen foods become active again when food is brought to room temperature. Thoroughly cooking food kills bacteria.
Many types of bacteria cause foodborne illnesses. Examples include
Viruses are tiny capsules, much smaller than bacteria, that contain genetic material. Viruses cause infections that can lead to sickness. People can pass viruses to each other. Viruses are present in the stool or vomit of people who are infected. People who are infected with a virus may contaminate food and drinks, especially if they do not wash their hands thoroughly after using the bathroom.
Common sources of foodborne viruses include
Common foodborne viruses include
Parasites are tiny organisms that live inside another organism. In developed countries such as the United States, parasitic infections are relatively rare.
Cryptosporidium parvum and Giardia intestinalis are parasites that are spread through water contaminated with the stools of people or animals who are infected. Foods that come into contact with contaminated water during growth or preparation can become contaminated with these parasites. Food preparers who are infected with these parasites can also contaminate foods if they do not thoroughly wash their hands after using the bathroom and before handling food.
Trichinella spiralis is a type of roundworm parasite. People may be infected with this parasite by consuming raw or undercooked pork or wild game.
Harmful chemicals that cause illness may contaminate foods such as
Anyone can get a foodborne illness. However, some people are more likely to develop foodborne illnesses than others, including
These groups also have a greater risk of developing severe symptoms or complications of foodborne illnesses.
Symptoms of foodborne illnesses depend on the cause. Common symptoms of many foodborne illnesses include
Symptoms can range from mild to serious and can last from a few hours to several days.
C. botulinum and some chemicals affect the nervous system, causing symptoms such as
Foodborne illnesses may lead to dehydration, hemolytic uremic syndrome (HUS), and other complications. Acute foodborne illnesses may also lead to chronic—or long lasting—health problems.
When someone does not drink enough fluids to replace those that are lost through vomiting and diarrhea, dehydration can result. When dehydrated, the body lacks enough fluid and electrolytes—minerals in salts, including sodium, potassium, and chloride—to function properly. Infants, children, older adults, and people with weak immune systems have the greatest risk of becoming dehydrated.
Signs of dehydration are
Signs of dehydration in infants and young children are
Also, when people are dehydrated, their skin does not flatten back to normal right away after being gently pinched and released.
Severe dehydration may require intravenous fluids and hospitalization. Untreated severe dehydration can cause serious health problems such as organ damage, shock, or coma—a sleeplike state in which a person is not conscious.
Hemolytic uremic syndrome is a rare disease that mostly affects children younger than 10 years of age. HUS develops when E. coli bacteria lodged in the digestive tract make toxins that enter the bloodstream. The toxins start to destroy red blood cells, which help the blood to clot, and the lining of the blood vessels.
In the United States, E. coli O157:H7 infection is the most common cause of HUS, but infection with other strains of E. coli, other bacteria, and viruses may also cause HUS. A recent study found that about 6 percent of people with E. coli O157:H7 infections developed HUS. Children younger than age 5 have the highest risk, but females and people age 60 and older also have increased risk.3
Symptoms of E. coli O157:H7 infection include diarrhea, which may be bloody, and abdominal pain, often accompanied by nausea, vomiting, and fever. Up to a week after E. coli symptoms appear, symptoms of HUS may develop, including irritability, paleness, and decreased urination. HUS may lead to acute renal failure, which is a sudden and temporary loss of kidney function. HUS may also affect other organs and the central nervous system. 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. Older adults had the highest mortality rate—about one-third of people age 60 and older who developed HUS died.3
Studies have shown that some children who recover from HUS develop chronic complications, including kidney problems, high blood pressure, and diabetes.
Some foodborne illnesses lead to other serious complications. For example, C. botulinum and certain chemicals in fish and seafood can paralyze the muscles that control breathing. L. monocytogenes can cause spontaneous abortion or stillbirth in pregnant women.
Research suggests that acute foodborne illnesses may lead to chronic disorders, including
A recent study found that adults who had recovered from E. coli O157:H7 infections had increased risks of high blood pressure, kidney problems, and cardiovascular disease.7
People with any of the following symptoms should see a health care provider immediately:
If a child has a foodborne illness, parents or guardians should not hesitate to call a health care provider for advice.
To diagnose foodborne illnesses, health care providers ask about symptoms, foods and beverages recently consumed, and medical history. Health care providers will also perform a physical examination to look for signs of illness.
Diagnostic tests for foodborne illnesses may include a stool culture, in which a sample of stool is analyzed in a laboratory to check for signs of infections or diseases. A sample of vomit or a sample of the suspected food, if available, may also be tested. A health care provider may perform additional medical tests to rule out diseases and disorders that cause symptoms similar to the symptoms of foodborne illnesses.
If symptoms of foodborne illnesses are mild and last only a short time, diagnostic tests are usually not necessary.
The only treatment needed for most foodborne illnesses is replacing lost fluids and electrolytes to prevent dehydration.
Over-the-counter medications such as loperamide (Imodium) and bismuth subsalicylate (Pepto-Bismol and Kaopectate) may help stop diarrhea in adults. However, people with bloody diarrhea—a sign of bacterial or parasitic infection—should not use these medications. 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 lifethreatening symptoms and complications, such as paralysis, severe dehydration, and HUS.
The following steps may help relieve the symptoms of foodborne illnesses and prevent dehydration in adults:
Infants and children present special concerns. Infants and children 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:
Older adults and adults with weak immune systems should also drink oral rehydration solutions to prevent dehydration.
Foodborne illnesses can be prevented by properly storing, cooking, cleaning, and handling foods.
More information about preventing foodborne illnesses is available at www.foodsafety.gov.
People who visit certain foreign countries are at risk for traveler’s diarrhea, which is caused by eating food or drinking water contaminated with bacteria, viruses, or parasites. Traveler’s diarrhea can be a problem for people traveling to developing countries in Africa, Asia, Latin America, and the Caribbean. Visitors to Canada, most European countries, Japan, Australia, and New Zealand do not face much risk for traveler’s diarrhea.
To prevent traveler’s diarrhea, people traveling from the United States to developing countries should avoid
Travelers can drink bottled water, bottled soft drinks, and hot drinks such as coffee or tea.
People concerned about traveler’s diarrhea should talk with a health care provider before traveling. The health care provider may recommend that travelers bring medication with them in case they develop diarrhea during their trip. Health care providers may advise some people—especially people with weakened immune systems—to take antibiotics before and during a trip to help prevent traveler’s diarrhea. Early treatment with antibiotics can shorten a bout of traveler’s diarrhea.
The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and other components of the National Institutes of Health (NIH) conduct and support research into many diseases and conditions.
Clinical trials are part of clinical research and at the heart of all medical advances. Clinical trials look at new ways to prevent, detect, or treat disease. Researchers also use clinical trials to look at other aspects of care, such as improving the quality of life for people with chronic illnesses. Find out if clinical trials are right for you.
Clinical trials that are currently open and are recruiting can be viewed at www.ClinicalTrials.gov.
This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.
The NIDDK would like to thank:
Howard Trachtman, M.D., Long Island Jewish Medical Center; Peter McNally, M.D., American College of Gastroenterology; Howard Sutter, U.S. Food and Drug Administration; Peter McNally, M.D., American College of Gastroenterology; Howard Sutter, U.S. Food and Drug Administration; Paul N. Maton, M.D., Digestive Disease Specialists, Oklahoma City, OK