Food poisoning, sometimes called foodborne illness, is a common but preventable condition caused by eating foods contaminated with harmful pathogens.

According to the Centers for Disease Control and Prevention (CDC), every year, 1 in 6 Americans experience food poisoning.

The most common symptoms are nausea, vomiting, abdominal cramping, and diarrhea.

Many cases of food poisoning are mild and get better on their own. Severe or chronic cases, however, may require medical intervention.

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Food poisoning may affect 1 in 6 Americans every year due to contaminated food containing pathogens.

Food poisoning is caused by eating food contaminated with pathogens, which are infectious bacteria, parasites, or viruses. Most foodborne illnesses are gastrointestinal, meaning they cause symptoms in the digestive tract.

Despite major advances in food production and safety, food poisoning is still very common. Food contamination can occur during production, processing, transportation, and storage. Contamination also happens during preparation and cooking.

A 2013 study found that 51 percent of food poisoning cases were caused by plant products and 48 percent were caused by animal products, including beef, pork, poultry, and seafood. This data was pulled from a 10-year period from 1998-2008.

A CDC study found that, out of the 9 million annual cases of food poisoning in the United States (U.S.), roughly 56,000 required hospitalization and 1,350 led to death.

Common causes of food poisoning include:

Norovirus

Norovirus is a contagious virus found in food and water contaminated with feces. It can spread through contact with infected individuals or surfaces.

Noroviruses are responsible for 58 percent of cases of foodborne illness in the U.S. In a CDC study, norovirus accounted for 26 percent of cases that required hospitalization.

Most outbreaks occur in food service settings, such as restaurants, where infected individuals have handled raw foods.

Norovirus does not have a cure. It is treated by a person resting, being hydrated, and taking vitamin and mineral supplements.

Most symptoms of norovirus infections begin within 12 to 48 hours of exposure. They usually stop after a few days.

Common norovirus symptoms include:

  • nausea
  • vomiting
  • diarrhea, usually constant and severe
  • stomach pain
  • abdominal cramping
  • fever
  • chills
  • headache
  • exhaustion
  • body aches or muscle soreness

In extreme cases, norovirus can cause severe dehydration. Without treatment, severe dehydration can lead to death.

Signs of severe dehydration include:

  • dizziness, especially when standing up
  • feeling faint or weak
  • extreme fatigue
  • dry mouth and throat
  • decreased urination
  • muscle pain or weakness
  • dry, sensitive, or painful eyes
  • unusual sleepiness, fussiness, and reduced tears in children

Nontyphoidal Salmonella

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Salmonella spreads through contaminated food and water, and causes infectious diarrhea.

Salmonella species are a leading cause of bacterial diarrhea worldwide, causing 94 million cases and around 115,000 deaths every year.

According to a 2011 CDC study, nontyphoidal Salmonella is responsible for 11 percent of American food poisoning cases and 35 percent of food illness hospitalizations annually.

Salmonella spreads through food and water contaminated with fecal matter. Contact with infected individuals or animals can also cause infection.

Salmonella infections most commonly cause infectious diarrhea (gastroenteritis). Other common symptoms include fever and abdominal pain.

Symptoms can start at any point within 6 to 72 hours of exposure but commonly occur within 12 to 36 hours. Diagnosis is usually made using a fecal sample.

In many cases, hydration and rest are the only recommended treatment. Most infections get better within 4 to 7 days.

Severe cases or high-risk individuals, such as children, older people, and people with weakened immune systems, may be given antimicrobial medications.

Clostridium perfringens

Clostridium perfringens is a type of bacteria that infects the intestines of humans and animals. Illness occurs if a large amount of the bacteria is consumed. It cannot be spread through contact with an infected person.

Most commonly found in raw meat and poultry products, Clostridium perfringens spreads in pre-cooked foods that have been kept warm for serving.

According to the CDC study, Clostridium perfringens is responsible for 10 percent of food poisoning cases in the U.S.

Infection can occur at any point between 6 to 24 hours after exposure but usually happens within 8 to 12 hours.

Symptoms include diarrhea and abdominal pain. Most people do not experience fever or vomiting. Symptoms often begin suddenly and stop within 24 hours.

Most cases are treated with rest and hydration. For severe cases, electrolyte replacement and intravenous fluids may be necessary to avoid severe dehydration.

Campylobacter species

Campylobacter species are the leading global cause of bacterial gastroenteritis, or inflammation of the stomach and small intestines.

They are found in the intestines of warm-blooded animals, especially cattle and poultry, and spread through the consumption of meat and poultry products. They can also spread through direct contact with infected animals.

According to a CDC study, Campylobacter species are responsible for 9 percent of U.S. cases of food poisoning and 15 percent of hospitalizations annually.

Infection can occur 1 to 10 days after exposure. Most infections are mild and improve on their own within 3 to 6 days.

The most common symptoms include:

  • diarrhea
  • nausea
  • vomiting
  • fever
  • abdominal pain or cramping
  • headache
  • fatigue
  • dehydration

Treatment includes hydration and rest. Children, older adults, and people with a weakened immune system may require medical attention.

Parasites

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Undercooked meat and fish that has been contaminated with feces may transmit parasites.

There are many parasites that can be transmitted through contaminated food. The CDC report that the most common foodborne parasites in the U.S. are:

  • protozoa, such as Cryptosporidium species and Toxoplasma gondii
  • roundworms, such as Trichinella species
  • tapeworms, such as Diphyllobothrium

T. gondii is estimated to be the cause of 8 percent of hospitalizations and 24 percent of deaths related to food poisoning in the U.S.

These parasites can be transmitted through undercooked meat and fish and raw vegetables that have been contaminated with feces.

Symptoms vary depending on the parasite. Many cause gastrointestinal symptoms, while some can also lead to a cough, skin lesions, and nerve problems.

Listeria monocytogenes

Although they are rarer than other forms of foodborne illness, Listeria monocytogenes infections are often serious and require hospitalization.

According to the CDC, around 1,600 people get Listeria infections each year, and 1 in 5 dies from the condition.

Listeria most commonly affects newborns, pregnant women, older adults, and those with immune system conditions.

Initial signs of infection include diarrhea, similar to most foodborne illnesses. Symptoms normally occur within 1 to 4 hours of consuming contaminated food.

If Listeria spreads, it can cause an invasive infection. Symptoms of an invasive infection include:

  • fever
  • muscle aches and pain
  • stiff muscles or joints, particularly in the neck
  • loss of balance
  • confusion
  • convulsions

In pregnant women, symptoms may include:

  • fever
  • flu-like symptoms

If these symptoms occur during pregnancy, seek immediate medical attention. The bacteria can spread to the fetus through the placenta, causing stillbirth.

Listeria is diagnosed using fecal samples and treated using antibiotics.

Escherichia coli (E. coli)

E. coli bacteria live naturally in the intestines of most healthy humans. While most types of E. coli are harmless, some species cause infections.

These bacteria spread through fecal matter in food or water, as well as through direct contact with infected individuals.

E.coli species can cause a wide variety of symptoms. These include:

  • diarrhea
  • bloody diarrhea
  • abdominal cramping
  • low-grade fever
  • dehydration
  • urinary tract infection (UTI)
  • respiratory infection

Most symptoms appear within 3 to 4 days of infection and improve after 5 to 7 days.

The recommended treatment is usually hydration and rest. However, a few species of E. coli can cause bloody diarrhea and severe dehydration, which require hospitalization or more immediate medical treatment.

Many cases of food poisoning are preventable.

Good hygiene and cooking foods thoroughly are the best and easiest ways to avoid food poisoning.

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Food poisoning can be prevented if some rules are followed, such as reheating food to the correct temperature and avoiding cross-contaminating food.

Safe minimum cooking temperatures include:

  • ground meats: 160°F
  • fresh beef, veal, and lamb: 145°F (let stand 3 minutes)
  • poultry: 165°F
  • pork and ham: 145°F (let stand 3 minutes)
  • egg dishes: 160°F, cook eggs until whites are firm
  • leftover dishes and casseroles: 165°F
  • fish: 145°F or flesh can come apart with a fork
  • shellfish: cook until shells open on their own

Some ways to prevent food poisoning include:

  • frequent hand-washing
  • refrigerating perishable foods within 1 hour and cooked foods within 2 hours
  • reheating foods to recommended cooking temperatures
  • avoiding touching your face or mouth
  • washing fruits and vegetables before cooking and consumption
  • avoiding cross contamination of meats, poultry, and dairy products with fruits and vegetables
  • keeping diapers, dog bags, and cat litter away from food preparation areas
  • avoiding exposure to small, uncirculated bodies of water, such as small lakes, ponds, and children's play pools
  • washing hands frequently when around farm and zoo animals

Take precautions when eating raw foods and foods that have been prepared commercially, as well as foods that have been left out of the refrigerator, sitting on ice, under heat lamps, or on heating plates.

If you have symptoms of food poisoning or suspect exposure to foodborne illnesses, avoid contact with others or preparing food for others.