Common causes of food poisoning

Millions of Americans deal with the misery of food poisoning each year, and a new report looks at some of the most common germs that made people sick in 2017.

The report, published yesterday (March 22) by the Centers for Disease Control and Prevention (CDC), analyzed information from a database that tracks food poisoning cases at 10 labs across the U.S. and covers 49 million people. The researchers looked for nine pathogens commonly transmitted by food, including seven types of bacteria and two types of parasites.

The most commonly reported foodborne illness germ was Campylobacter, a bacterium that is often found in raw poultry. There were about 19 Campylobacter infections per 100,000 people in 2017, according to the report.

The second-most-common germ was Salmonella, which caused about 16 infections per 100,000 people, followed by Shigella and Shiga toxin-producing E. coli (STEC), each of which caused about 4 infections per 100,000 people.

There was a 10-percent increase in the rate of Campylobacter infections and a 28-percent increase in the rate of STEC infections in 2017, compared with 2014-2016, the report found. However, some of these increases may have been due to the use of a relatively new type of lab test, called culture-independent diagnostic tests, which allow researchers to test for foodborne pathogens by looking for proteins or genetic material tied to the pathogens, rather than growing the germs in lab dishes. These tests can detect bacteria and other pathogens more easily than older tests, and are being used more and more frequently, the report said.

But researchers did see a 35-percent decrease in infections with E. coli O157, a type of STEC, in 2017 compared with 2006-2008, which mirrors a drop in E. coli O157 germs detected in ground beef over the same period, the report said.

The overall rate of Salmonella infections was about the same in 2017 as it was in 2014-2016, but there was a drop in the rate of infections with two particular strains of Salmonella, called typhimurium and Heidelberg. These declines may be due, in part, to steps to vaccinate chickens against these strains of Salmonella, as well as other measures to prevent contamination of meat products, the report said.

The researchers concluded that “more control measures are needed” to prevent foodborne illness, including possibly “new or revised meat and poultry performance standards, and enhanced training and guidance for industry and inspection personnel.”

The CDC estimates that 48 million people in the United States get sick with foodborne illness each year. The new report did not include rates of norovirus infection, which causes an estimated 20 million cases of illness each year.

Original article on Live Science.

Common Causes

In 4 out of 5 cases of food poisoning, you never find out exactly what caused it. That’s OK because you most likely will get better on your own. But in cases where the culprit is found, it’s usually one of the following:

  • Norovirus , often called stomach flu, is behind more than half of the foodborne illnesses in the U.S. where the cause is known. Norovirus can sicken you not only through eating contaminated foods, but also through touching doorknobs and other surfaces or having contact with an infected person. You should wipe down the kitchen if someone in your house has it. It typically takes 12-48 hours before you feel sick. Your symptoms may last 1-3 days.
  • Salmonella is the name of a group of bacteria. They grow in undercooked eggs and meat. But you can also get salmonella from unpasteurized milk or cheese. Some fruits and vegetables, such as melons or sprouts, can also cause it. Symptoms start within 1-3 days and can last up to a week.
  • Clostridium perfringens are bacteria that are more likely to show up when foods are prepared in bulk, such as in cafeterias or nursing homes or for catered events. Cooking kills the bacteria but not its spores. So food left warming can grow new germs. You can get it from beef, chicken, or gravy. You may have cramps and diarrhea but no other symptoms. You get sick within 6-24 hours and are usually feeling better in a couple of days.
  • Campylobacter comes from undercooked poultry, unpasteurized milk, and sometimes water. It may take 2-5 days to develop symptoms you can notice. But you should feel better in another 2-10 days. You can’t pass it to anyone. But if it’s serious, you might have bloody diarrhea.

Symptoms & Causes of Food Poisoning

On this page:

  • What are the symptoms of food poisoning?
  • What are the symptoms of dehydration?
  • Seek care right away
  • What causes food poisoning?
  • What kinds of microbes cause food poisoning?
  • How do harmful chemicals cause food poisoning?

What are the symptoms of food poisoning?

Common symptoms of food poisoning include

  • diarrhea or bloody diarrhea
  • vomiting
  • pain in your abdomen
  • fever
  • headache

Symptoms range from mild to severe and may last from a few hours to several days.

Less commonly, some types of food poisoning—such as botulism and fish and shellfish poisoning—can affect your nervous system. Symptoms may include

  • blurred vision
  • headache
  • paralysis
  • tingling or numbness of your skin
  • weakness

People with nervous system symptoms should see a doctor or go to an emergency room right away.

What are the symptoms of dehydration?

Symptoms of dehydration, the most common complication of food poisoning, may include the following in adults

  • extreme thirst and dry mouth
  • urinating less than usual
  • light-headedness; dizziness, which may occur when the person stands up; or fainting
  • feeling tired
  • dark-colored urine
  • decreased skin turgor, meaning that when you pinch and release the person’s skin, it does not flatten back to normal right away
  • sunken eyes or cheeks

If you are the parent or caretaker of an infant or a young child with symptoms of food poisoning, you should watch for the following signs of dehydration

  • thirst and dry mouth
  • urinating less than usual, or no wet diapers for 3 hours or more
  • lack of energy
  • no tears when crying
  • decreased skin turgor, meaning that when you pinch and release the child’s skin, it does not flatten back to normal right away
  • sunken eyes or cheeks

Anyone with signs or symptoms of dehydration should see a doctor or go to an emergency room right away. A person with severe dehydration may need treatment at a hospital.

Seek care right away

Food poisoning can become dangerous if it leads to severe dehydration or other complications. The symptoms listed below may suggest that an adult or child has a severe form of food poisoning, dehydration or other complications, or a serious health problem other than food poisoning. Anyone with these signs or symptoms should see a doctor right away.


Adults with any of the following symptoms should see a doctor right away

  • change in mental state, such as irritability, lack of energy, or confusion
  • high fever
  • vomiting often
  • six or more loose stools in a single day
  • diarrhea that continues for more than 3 days
  • nervous system symptoms
  • severe pain in the abdomen or rectum
  • stools that are black and tarry or contain blood or pus
  • symptoms of dehydration or other complications

Adults should also see a doctor if they aren’t able to drink enough liquids or oral rehydration solutions—such as Pedialyte, Naturalyte, Infalyte, and CeraLyte—to prevent dehydration or if they do not improve after drinking oral rehydration solutions.

Older adults, pregnant women, and adults with a weakened immune system or another health condition should also see a doctor right away if they have any symptoms of food poisoning.

Infants and children

If an infant or child has signs or symptoms of food poisoning, don’t hesitate to call a doctor for advice. Diarrhea is especially dangerous in newborns and infants, leading to severe dehydration in just a day or two. A child with symptoms of dehydration can die within a day if left untreated.

If you are the parent or caretaker of an infant or child with any of the following signs or symptoms, seek a doctor’s help right away

  • change in the child’s mental state, such as irritability or lack of energy
  • diarrhea lasting more than a day
  • any fever in infants
  • high fever in older children
  • frequent loose stools
  • vomiting often
  • nervous system symptoms
  • severe pain in the abdomen or rectum
  • signs or symptoms of complications, such as dehydration or hemolytic uremic syndrome
  • stools that are black and tarry or contain blood or pus

You should also seek a doctor’s help right away if a child has signs or symptoms of food poisoning and the child is an infant, was born prematurely, or has a history of other medical conditions. Also seek a doctor’s help right away if the child is not able to drink enough liquids or oral rehydration solutions to prevent dehydration or if the child does not improve after drinking oral rehydration solutions.

If a child has signs or symptoms of food poisoning, don’t hesitate to call a doctor for advice.

What causes food poisoning?

Infections with microbes—viruses, bacteria, and parasites—cause most food poisoning.2 Harmful chemicals also cause some cases of food poisoning.

Microbes can spread to food at any time while the food is grown, harvested or slaughtered, processed, stored, shipped, or prepared.

Some harmful microbes may already be present in foods when you buy them. Foods that may contain microbes include

  • fresh produce
  • raw or undercooked meat, poultry, and eggs
  • dairy products and fruit juices that have not been pasteurized—heated to kill harmful microbes
  • fish and shellfish
  • foods that people handle during preparation, sometimes called “deli foods,” such as sliced meat, salads and cut fruit, sandwiches, and baked goods
  • processed and ready-to-eat meats such as hot dogs or deli meat
  • foods that are not properly canned or sealed

If you don’t keep raw foods—such as beef, poultry, seafood, and eggs—separate from other foods, microbes from the raw foods can spread to other foods. Microbes can also spread from raw foods to your hands, kitchen utensils, cutting boards, and kitchen surfaces during food preparation. If you don’t wash your hands, utensils, cutting boards, and surfaces completely after they have come into contact with raw foods, they can spread microbes to other foods.

If you don’t wash your hands completely after they have come into contact with raw foods, they can spread microbes to other foods.

Microbes can cause food poisoning if you don’t take steps to kill or slow the growth of microbes in food. Microbes can grow if people don’t cook food thoroughly, keep cooked food hot, or promptly refrigerate or freeze food that can spoil.

Microbes present in the stool or vomit of people who are infected can also spread to food and cause food poisoning. People may spread these microbes to foods and drinks, especially if they don’t wash their hands thoroughly after using the bathroom, after changing a diaper, and before preparing foods and drinks.

Find tips to keep food safe and help prevent food poisoning.

What kinds of microbes cause food poisoning?


Viruses invade normal cells in your body. Many viruses cause infections that can be spread from person to person.

If water comes into contact with stools of infected people, the water may become contaminated with a virus. The contaminated water can spread the virus to foods. For example, if contaminated water is used to water or wash produce, the virus can spread to the produce. Similarly, shellfish that were living in contaminated water could contain a virus.

If people who are infected with a virus prepare or handle foods, they may spread the virus to the foods.

Common viruses that cause food poisoning include norovirus and hepatitis A.


Bacteria are tiny organisms that can cause infection or disease. Bacteria can enter your body through contaminated food or water.

Bacteria grow quickly when the temperature of food is between 40 and 140 degrees. Keeping food colder than 40 degrees in a refrigerator or freezer can slow or stop the growth of bacteria. Cooking food thoroughly often kills bacteria.

Many types of bacteria can cause food poisoning, including

  • certain types of Salmonella
  • certain types of Clostridium, including the common C. perfringens and the less common C. botulinum, which causes an illness called botulism
  • certain types of Campylobacter, including C. jejuni
  • Staphylococcus aureus, also called staph
  • Escherichia coli, also called E. coli
  • certain types of Vibrio
  • Listeria monocytogenes, also called Listeria


Parasites are tiny organisms that live inside other organisms. Parasites can enter your body through food or water and settle in your digestive tract. In developed countries such as the United States, parasitic infections are rare.

Parasites that cause food poisoning include

  • Toxoplasma gondii, which causes an illness called toxoplasmosis
  • Giardia
  • Cryptosporidium, which causes an illness called cryptosporidiosis or crypto

Travelers’ diarrhea

People who travel from the United States to developing countries may develop travelers’ diarrhea. Eating food or drinking water contaminated with bacteria, parasites, or viruses causes travelers’ diarrhea. Although travelers’ diarrhea is most often acute, some parasites cause diarrhea that lasts longer.

How do harmful chemicals cause food poisoning?

Harmful chemicals may be present in certain foods, including

  • fish and shellfish that contain toxins produced by algae or bacteria
  • certain types of wild mushrooms
  • unwashed produce that contains large amounts of chemical pesticides

According to the Centers for Disease Control and Prevention, approximately 48 million Americans get sick, 128,000 are hospitalized and 3,000 die each year from food poisoning.

Bacteria, viruses and parasites are the sources of many food poisoning cases, usually due to improper food handling. Some bacteria, in small amounts, are not harmful to most healthy adults because the human body is equipped to fight them off. The trouble begins when certain bacteria and other harmful pathogens multiply and spread, which can happen when food is mishandled. Foods that are contaminated may not look, taste or smell any different from foods that are safe to eat. Symptoms of food poisoning vary and develop as quickly as 30 minutes to as long as several days after eating food that’s been infected.

As identified by the CDC, eight known pathogens (bacteria, viruses and parasites) account for the majority of foodborne illness, hospitalization and death in the United States.


Salmonella is the name of a group of bacteria that causes the infection salmonellosis. It is one of the most common bacterial causes of diarrhea and the most common cause of foodborne-related hospitalizations and deaths. Salmonella is more severe in pregnant women, older adults, younger children and those with a weakened immune system. Because Salmonella bacteria can live in the intestinal tract of humans and other animals, it can spread easily unless you use proper hygiene and appropriate cooking methods.

Sources: You can contract salmonellosis by consuming raw and undercooked eggs, undercooked poultry and meat, contaminated raw fruits and vegetables (such as sprouts and melons), as well as raw milk and other dairy products that are made with unpasteurized milk. It also can be transmitted through contact with infected animals or infected food handlers who have not washed their hands after using the bathroom.

Prevention: Cook foods such as eggs, poultry and ground beef, thoroughly, to their recommended internal temperatures. Wash raw fruit and vegetables before peeling, cutting or eating. Avoid unpasteurized dairy products and raw or undercooked meats, poultry and seafood. Wash hands often, especially after handling raw meat or poultry. Clean kitchen surfaces and avoid cross-contamination.

Clostridium perfringens

Clostridium perfringens, also known as C. perfringens, is very common in our environment. It can multiply very quickly under ideal conditions. Infants, young children and older adults are most at risk.

Sources: Illness usually occurs by eating foods contaminated with large numbers of this bacteria that produce enough toxin to cause sickness in the form of abdominal cramping and diarrhea. C. perfringens is sometimes referred to as the “buffet germ” because it grows fastest in large portions of food, such as casseroles, stews and gravies that have been sitting at room temperature in the danger zone. If food isn’t originally cooked, reheated or kept at the appropriate temperature, live bacteria may be consumed and cause illness.

Prevention: Cook food thoroughly and keep it out of the danger zone, above a temperature of 140°F or below 40°F. Practice leftover safety by dividing roasts and stews into smaller quantities for faster cooling and refrigerate right away. Leftovers should be reheated to an internal temperature of 165°F or higher before serving. However, any foods left out at room temperature for more than two hours should be thrown out and after only one hour if it’s 90 degrees or warmer.


Campylobacter is a common cause of diarrhea. Most cases of campylobacteriosis, the infection caused by Campylobacter bacteria, are associated with eating raw or undercooked poultry and meat or from cross-contamination of other foods by these items. Freezing reduces the number of Campylobacter bacteria on raw meat but will not kill them completely, so proper heating of foods is important. Campylobacteriosis occurs more frequently in the summer and is most common in infants and young children.

Sources: Sources include consuming raw and undercooked poultry and other meats, unpasteurized dairy products and untreated water or contaminated produce.

Prevention: Cook all foods thoroughly to their appropriate internal temperatures, prevent cross-contamination by using separate cutting boards when handling raw and cooked foods, don’t drink unpasteurized milk or untreated water and wash hands frequently. Wash raw fruits and vegetables before peeling, cutting and eating.

Staphylococcus aureus

Staphylococcus aureus (staph) is commonly found on the skin, throats and nostrils of healthy people and animals. Therefore, it usually doesn’t cause illness unless it is transmitted to food products where it can multiply and produce harmful toxins. Staphylococcal symptoms include nausea, stomach cramps, vomiting or diarrhea. Staphylococcal bacteria can be destroyed by cooking but their toxins are heat resistant and cannot. Anyone can develop a staph infection but certain groups of people are at greater risk, including people with chronic conditions such as diabetes, cancer, vascular disease, eczema and lung disease.

Sources: The bacteria can be found in unpasteurized dairy products and salty foods such as ham and other sliced meats. Foods that are made or come in contact with hands and require no additional cooking are at highest risk, including:

  • Salads, such as ham, egg, tuna, chicken, potato and macaroni
  • Bakery products, such as cream-filled pastries, cream pies and chocolate éclairs
  • Sandwiches.

Prevention: Keep foods out of the temperature danger zone and keep kitchen areas clean. Wash hands with soap and water, do not prepare or serve food if you have a nose or eye infection or if you have wounds or skin infections on your hands or wrists.

E. coli O157:H7

Escherichia coli, better known as E. coli, are a large group of bacteria. Although most strains of E. coli are harmless, some can make you very sick. One strain, E. Coli O157:H7 (STEC) is commonly associated with food poisoning outbreaks because its effects can be extremely severe.

Sources: These include eating raw or undercooked ground beef or drinking unpasteurized beverages or dairy products.

Prevention: Wash your hands, cook meat (especially ground meat) and poultry thoroughly to their appropriate internal temperatures; avoid unpasteurized dairy products, juices or ciders; keep cooking surfaces clean; and prevent cross-contamination. Also, don’t swallow water when playing or swimming in lakes, ponds, streams or pools.

Listeria monocytogenes

Eating food contaminated with Listeria monocytogenes bacteria causes listeriosis — a serious infection that primarily affects individuals who are at a high risk for food poisoning: older adults, pregnant women, young children and people with weakened immune systems. Listeria can grow at refrigerator temperatures where most other bacteria cannot grow.

Causes: Listeria is found in refrigerated, ready-to-eat foods such as hot dogs, deli meats, unpasteurized milk, raw sprouts, dairy products and raw and undercooked meat, poultry and seafood.

Prevention: Cook all foods to proper internal temperatures and reheat precooked foods to 165°F; wash raw fruits and vegetables before peeling, cutting or eating; separate uncooked meats and poultry from foods that are already cooked or ready-to-eat; wash hands thoroughly; store foods safely by making sure the temperature in your refrigerator is at or below 40F; maintain a clean refrigerator and kitchen area; and wash reusable grocery totes regularly.


Norovirus is one of the leading causes of food poisoning and often results in symptoms similar to stomach flu such as stomach cramping, nausea, vomiting and diarrhea. Norovirus spreads easily by coming in contact with someone who is infected, especially in crowded areas. Foods, drinks and surfaces also can become contaminated with the norovirus. Anyone can get sick with norovirus, but the illness can be especially serious for young children and older adults. You can contract norovirus many times in your life.

Sources: Fresh produce, shellfish, ice, fruit and ready-to-eat foods, especially salads, sandwiches and cookies that have been prepared by someone who is infected are sources of norovirus.

Prevention: Do not cook, prepare or serve foods or beverages while you are sick. Frequently wash your hands with soap and water for at least 20 seconds. Keep foods and utensils clean by washing all fruits and vegetables, cutting boards, knives, kitchen surface areas, table linens, cloth napkins and reusable grocery bags.

Toxoplasma gondii

Toxoplasma is a parasite that causes toxoplasmosis — a disease that can result in serious health problems in individuals who are at high risk for food poisoning: pregnant women, infants, older adults and people with weakened immune systems. Symptoms can be similar to flu and include swollen lymph glands or muscle aches and pains that last for months. Other symptoms affect the eyes, causing vision to be reduced or blurred or cause pain, redness or tearing.

Sources: Sources include eating undercooked, contaminated meat or using utensils or cutting boards that have had contact with raw meat; coming into contact with feces from an infected cat when cleaning the litter box; or drinking contaminated water. Toxoplasma also can be spread to infants if a mother has become infected before or while pregnant.

Prevention: Cook food to safe temperatures — a food thermometer should be used to ensure food has reached a safe internal temperature. Also, freeze meat properly; wash fruits and vegetables before peeling, cutting and eating; avoid unpasteurized dairy products; maintain clean cutting boards; and always wash your hands with soap and water. In addition, wear gloves when cleaning a cat’s litter box or touching soil in case it is contaminated with cat feces, especially if pregnant or are at a higher risk of getting sick.

One of the best things you can do to reduce your risk of food poisoning is to practice safe food handling at home. Consult a physician if you think you or someone else has been sickened by food poisoning.


What is salmonella?

Salmonella is one of the most common types of food poisoning caused by bacteria in the United States. The US Centers for Disease Control gets about 42,000 reports of salmonella each year. Experts there believe the total number of cases actually may be more than 1.2 million. Salmonella is more common in the summer than the winter.

Salmonella usually is a brief illness with stomach cramps and diarrhea that lasts four to seven days. In some people, the diarrhea can be severe or last longer. In general, children are more likely to get salmonella than other age groups.

Who is at risk for severe salmonella?

  • Older people (age 65 and older)
  • Infants
  • People with weak immune systems (cancer patients, frail elderly people, people with HIV or AIDS).
  • People with inflammatory bowel disease (Ulcerative Colitis or Crohn’s Disease)

How does a person get salmonella?

Salmonella are a type of bacteria that can live in the digestive tract (intestines) of humans and other animals. Salmonella can pass out of the intestines into poop (feces/stool). A person can get infected with Salmonella by:

  • Eating undercooked foods contaminated with animal feces.
    • Cooking food destroys Salmonella. Eating raw or undercooked beef, poultry (like chicken or duck), and seafood are a risk. Foods that contain raw eggs also are a risk (like cookie dough or homemade mayonnaise).
    • Milk and unwashed, raw vegetables and fruit also can carry Salmonella.
  • Eating food prepared on surfaces that were in contact with raw meat (such as a cutting board, or countertop).
  • Eating foods contaminated with human feces.
    • This can happen if a food worker does not wash his or her hands before handling food.
  • Holding, kissing or petting turtles, snakes, lizards, chicks and baby birds.
    • These animals are likely to carry Salmonella. People can get infected if they do not wash their hands after they handle these animals or touch their feces or environment (cage, pen, ground, etc.).
    • FYI: In 1975 the US Food and Drug Administration banned the sale of small turtles in the United States because of the risk of salmonella.

What are the symptoms of salmonella?

  • Diarrhea, fever, and stomach cramps that develop 12 to 72 hours after infection
  • Headache
  • Nausea, vomiting, loss of appetite

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