Foodborne illness is a gastrointestinal infection caused by eating foods that contain harmful bacteria, viruses, parasites or toxins.

According to estimates by the U.S. Centers for Disease Control and Prevention (CDC), approximately 76 million cases of foodborne illness occur each year in the United States. These cases result in an estimated 325,000 hospitalizations and 5,000 deaths a year.

More than 250 foodborne diseases have been identified. Some of the most common types of foodborne illnesses include Campylobacteriosis (caused by Campylobacter bacteria), Salmonellosis (caused by Salmonella bacteria) and Calicivirus (Norwalk-like virus).

Food can become contaminated in a variety of ways during production and preparation. For example, beef and poultry can become contaminated during slaughter.

The most common signs and symptoms of foodborne illness include nausea, vomiting, diarrhea and abdominal cramps.

Foodborne illnesses can be difficult to diagnose. Diagnosis typically begins with a physical examination which includes a medical history and a list of recent foods consumed. Some types of foodborne illnesses are diagnosed by analyzing stool under a microscrope to detect the presence of bacteria.

Most cases of foodborne illness are mild and can be treated at home by replacing lost fluids and electrolytes, which are necessary to maintain the body’s chemical balance. More serious cases may be treated in a hospital where patients are given fluids intravenously (through a vein).

Foodborne illness can be prevented in a variety of ways. For example, foods that may become contaminated, such as meats and milk, should be stored in the freezer or the coldest parts of the refrigerator. Washing hands before and after food preparation, establishing separate cutting boards for meat and vegetables and thoroughly cooking beef and chicken are other ways to prevent foodborne illness.

Foodborne illnesses (commonly known as food poisoning) are gastrointestinal infections that occur when foods contaminated with harmful organisms are ingested.

Food can be contaminated by a number of pathogens (organisms that cause disease) including bacteria, viruses and parasites. The pathogen enters the body by the mouth and then travels into the stomach and intestines. After infection, an incubation period occurs, which may last from hours to days before symptoms appear.

Although rarer, foodborne illness can also be caused by toxins and chemicals. For instance, pesticides can remain on foods, which can cause illness. A naturally toxic substance, such as poisonous mushrooms, may be consumed, also causing sickness. Symptoms vary according to the source and may include nausea, vomiting, abdominal cramps and diarrhea.

The risk of acquiring foodborne illnesses is typically greater during the summer months because the warm weather speeds up bacterial growth on raw meats and poultry.

In most cases, foodborne illnesses are not serious and do not cause serious complications. However, certain types of illnesses such as botulism (severe food poisoning caused by a bacterial toxin) can result in serious health consequences (such as spontaneous abortion in pregnant women) or death.

In some people (especially children) a condition called hemolytic uremic syndrome (HUS) can result from infection by a particular strain of the E. coli bacteria. HUS is a rare disorder that usually affects children between ages 1 to 10. Although most children recover completely, it may cause acute renal (kidney) failure, seizures, heart failure, pancreatitis or, in rarer cases, diabetes.

The types of common foodborne illnesses can change over time. Typhoid fever, tuberculosis and cholera were once common foodborne diseases before food safety measures (such as pasteurization and safe food canning) became commonplace. In recent years, new foodborne illnesses have been discovered. In 1996, the parasite Cyclospora was identified as a cause of diarrhea that occurred after Guatemalan raspberries were consumed. In 1998, a new strain of the bacteria Vibrio parahaemolyticus contaminated oyster beds in Galveston Bay, Texas, and caused people that consumed the oysters to become ill.

Although local and state health departments are required to report cases of foodborne illness to the U.S. Centers for Disease Control and Prevention (CDC), establishing precise figures is difficult.  Most cases are not diagnosed because people do not seek treatment for the illness or physicians do not diagnose it. Therefore, the case is never reported to the CDC.

According to estimates by the CDC, there are approximately 76 million cases of foodborne illness each year in the United States. These cases result in an estimated 325,000 hospitalizations and 5,000 deaths annually.

In addition to tracking individual cases of foodborne illness, health departments keep track of outbreaks of foodborne illness. This occurs when a group of people eat the same contaminated food and two or more of them become sick. According to the CDC, about 400 to 500 outbreaks investigated by local and state health departments are reported each year.

Despite recent outbreaks, researchers report that the foods that Americans consume are now safer than in previous years.

More than 250 foodborne illnesses have been identified. Most of them are infections, caused by pathogens (organisms that cause disease) such as bacteria, viruses and parasites found in food. Others are poisonings caused by toxins or chemicals that have contaminated food, such as food served in lead-glazed pottery, or naturally poisonous foods, such as poisonous mushrooms.

The most common types of foodborne illnesses include:

• Campylobacteriosis. Caused by the Campylobacter bacteria, which is the most commonly identified bacteria that causes diarrhea. The bacteria live in the intestines of birds. Undercooked chicken or other foods are frequent sources of this type of infection.
  
  
• Clostridium perfringens infection. Results in diarrhea, abdominal pain, nausea and vomiting and usually develops after eating improperly stored or cooked meat.
  
  
• Salmonellosis. Caused by the Salmonella bacteria, which is widespread in the intestines of birds, reptiles and mammals. Any type of food can become contaminated with the salmonella bacteria. The foods that most frequently transmit salmonella are poultry, meat, eggs and dairy products. People may also be exposed to salmonella through contact with household pets - especially lizards, turtles, and snakes - and through contact with contaminated surfaces, such as computer keyboards and cooking utensils. Fever, diarrhea and abdominal cramps are common symptoms. In people with poor health or weakened immune systems, bacteria can enter the bloodstream and cause life-threatening infections. Some infected people do not develop symptoms, but instead become carriers and spread the infection to others.
  
  
• Escherichia coli (E. coli) infection. E. coli is a bacterial pathogen found in cattle and other related animals. Illness often occurs when people consume food (especially beef) or water that has been contaminated with microscopic amounts of cow feces. E. coli can also be spread through contact with contaminated surfaces and by touching infected animals (e.g., petting zoos). The illness causes severe diarrhea that may be bloody and painful abdominal cramps. In a small number of cases, a serious condition called hemolytic uremic syndrome (HUS) can occur. This can result in anemia, profuse bleeding and kidney failure.
  
  
• Calicivirus. An extremely common cause of viral foodborne illness. However, this type is rarely diagnosed because the laboratory test is not widely available. The virus (a type of norovirus) can spread from one person to another or through food.  For instance, a kitchen worker may spread the virus during food preparation.
  
  
• Shigellosis. Caused by the Shigella bacteria. It can be transmitted by eating food or drinking beverages contaminated by food handlers with Shigella, eating vegetables grown in fields containing sewage, eating food contaminated by flies bred in infected feces and drinking or swimming in contaminated water. The bacteria cause fever, bloody diarrhea and abdominal pain.
  
  
• Bacillus cereus food poisoning. Caused by the Bacillus cereus bacteria. It usually presents with extreme nausea and vomiting and has the fastest onset of symptoms (three hours) of foodborne illnesses. Bacillus cereus food poisoning is commonly seen in people after consuming Chinese fried rice.
  
  
• Staphylococcal food poisoning. Caused by the Staphylococcus aureus bacteria. Unlike other types of foodborne illness, this form is not caused by contamination. The bacteria can grow in some foods (e.g. dairy products, fish and processed meats) and produce a toxin that results in intense vomiting.
  
  
• Ascariasis (roundworm). A parasitic worm infection caused by contact with contaminated food or soil.
  
  
• Vibrio. There are many different types of this bacteria, one of which causes cholera. Other Vibrio species are commonly found in raw or undercooked shellfish. An infection often causes chills and fever.
  
  
• Giardiasis. Caused by the parasite Giardia that is passed to humans in drinking water or from infected animal products. Giardia is a common traveler’s illness which causes abdominal cramps and diarrhea.
  
  
• Chemical food poisoning. Some types of foods, such as certain species of mushrooms, contain toxins that result in illness. Most cases result in mild symptoms. However, some are more serious and require immediate medical treatment.
  
  
• Botulism. A rare, but serious illness caused by the Clostridium botulinum bacteria. If untreated, it can cause paralysis and respiratory failure. Cases of botulism are usually contracted from insufficiently heated home-canned foods, such as asparagus, green beans, beets and corn.

During production and preparation, food can become contaminated by pathogens (organisms that cause disease) in a variety of ways. Many foodborne microbes (microscopic organisms) are present in the intestines of animals raised for food, such as cows and chickens. Meat can become contaminated during slaughter if it comes into contact with intestines.

Fruits and vegetables can become contaminated if they are washed with water that is contaminated with animal manure or human sewage. Oysters and other filter-feeding shellfish can become contaminated with bacteria naturally present in sea water or with microbes present in human sewage dumped into the sea. Foods produced by the products of many individual animals (e.g., ground beef) can be readily contaminated because a pathogen from one animal can taint an entire batch of meat.

During food processing, food can become contaminated by infected humans who handle it. In the kitchen, microbes can be transferred between foods by knives, cutting boards or other utensils.

Food can also become contaminated after it is handled. Many types of bacterial microbes need to multiply before they reach levels that can cause illness. Bacteria multiply rapidly at temperatures between 40 and 140 degrees Fahrenheit (4 to 60 degrees Celsius). Therefore, foods contaminated with bacteria that are not refrigerated or cooked properly may cause illness. Food can also become contaminated after it is cooked if it comes into contact with other foods containing pathogens.

After microbes enter the body, symptoms appear after a period of time. This is called the incubation period, and it may last from hours to days depending on the type and quantity of microbes ingested. During the incubation period, the microbes move through the stomach to the intestine and attach to the intestinal walls, where they multiply. Some microbes remain in the intestine, others produce a toxin that enters the bloodstream and others penetrate deeper body tissues.

Some people are more susceptible to foodborne illnesses or may experience symptoms that are more severe. People who face a greater risk of developing foodborne illness include:

• Elderly people. As people age, their immune systems do not respond as quickly and effectively to infectious organisms.
  
  
• Infants and young children. The immune systems of very young people are not fully developed.
  
  
• People with weakened immune systems. People with certain conditions, such as the human immunodeficiency virus (HIV) or diabetes, have a greater risk of developing a foodborne illness.
  
  
• Pregnant women. Pregnant women have an increased risk of developing a foodborne illness after exposure to contaminated food.
  
  
• People exposed to a very high dose of a pathogen. 

The signs and symptoms of foodborne illness vary according to the type and amount of contaminant ingested. In most cases, the signs and symptoms resemble those of the stomach flu. They may range from mild to severe in intensity and may last a few hours to several days. They include:

• Abdominal cramps
• Nausea
• Vomiting
• Diarrhea (sometimes bloody)
• Fever
• Dehydration

In most cases, foodborne illnesses are not serious and the bacteria usually pass through the system in 24 to 48 hours. However, a physician should be consulted if:

• The patient is elderly, younger than age 3 or has a disease that weakens the immune system, such as cancer.
  
  
• Nausea, vomiting or diarrhea last longer than two days.
  
  
• Symptoms begin after foreign travel.
  
  
• Other friends or family members also experience symptoms after eating the same food.
  
  
• Liquids or medications cannot be kept in the stomach due to vomiting.
  
  
• The patient’s condition does not improve within two days despite drinking large amounts of fluid.
  
  
• Nervous system symptoms are present, such as slurred speech, muscle weakness, double vision or difficulty swallowing.

The following signs and symptoms may require immediate medical attention:

• Signs of shock, such as weak or rapid pulse, shallow breathing and shaking or chills.
  
  
• Signs of severe dehydration, such as dry mouth, decreased urine output and sunken eyes.
  
  
• Confusion or difficulty reasoning.

Foodborne illnesses may be diagnosed by a physician during a physical examination that includes a medical history and list of medications. A physician may ask a patient questions about:

• The types and amounts of foods eaten
  
• The locations where food was consumed (e.g., at home, in a restaurant)
  
• The symptoms experienced (e.g., nausea, vomiting, diarrhea)

Certain types of bacteria and parasites that cause foodborne illness (such as Campylobacter and Salmonella) can be detected with a laboratory test. Patients may be asked to provide a stool sample to be studied under a microscope for the presence of bacteria.

Many types of foodborne infections cannot be identified during routine laboratory tests and require specialized, experimental and/or expensive tests that are not widely available. For this reason, foodborne illnesses often go undiagnosed.

Treatment for foodborne illness varies according to the type and severity of the illness. Mild cases may be treated by replacing fluids and electrolytes (substances that are necessary for normal bodily chemistry and function) to avoid dehydration. Increasing fluid intake is particularly important for children because they become dehydrated faster than adults.

Tips for replacing fluids include:

• Begin by drinking small amounts of clear liquids (4 or more ounces each hour) if it can be tolerated. Soft drinks, tea, coffee, fruit juice and sports drinks should be avoided because they do not replace electrolytes appropriately.
  
  
• If diarrhea is severe (especially in children), drink oral rehydration solutions (fluids that contain glucose and electrolytes).
  
  
• Antidiarrheal medications may be taken to ease symptoms of diarrhea. However, these medications should be avoided in patients experiencing a high fever or blood in the stools.

After diarrhea and vomiting subsides, patients may start to gradually eat solid foods. Some diet tips include:

• Eat foods that contain salt, such as crackers or pretzels, to replace lost sodium.
  
  
• Eat foods such as oatmeal, white rice, applesauce and bananas to help slow down bowel movements.
  
  
• Eat foods that are easy to digest, such as chicken noodle soup or chicken rice soup.
  
  
• Avoid foods such as apple juice and chewing gum, which contain sorbitol, a sugar alcohol that worsens diarrhea.
  
  
• Limit intake of fatty and greasy foods (e.g., pizza) and high-fiber foods (e.g., bran cereal, whole grain breads, beans) because they may worsen diarrhea.

Severe cases of foodborne illness may require hospitalization. Patients may receive fluids intravenously (through a vein). Patients may be given antidiarrheal medications to ease diarrhea or antiemetics to treat nausea and/or vomiting. Patients are rarely given antibiotics to treat food poisoning. There are only a few types of foodborne illness (e.g., shigellosis) that respond to antibiotic treatment, and antibiotics can worsen some types of foodborne illness.

There are a number of ways to prevent foodborne illness, which include methods for food purchasing, storage and preparation. There are also specific ways to prevent foodborne illness while traveling.

Tips for buying food include:

• Never buy packages with tears or leaks.
  
  
• Do not buy foods past their expiration date.
  
  
• Do not buy produce that appears bruised or otherwise damaged.
  
  
• Do not buy fresh-cut produce that has not been refrigerated or stored in ice.
  
  
• Keep raw beef, pork and poultry separate from other foods.
  
  
• Put refrigerated or frozen items in the shopping cart last, right before checking out.
  
  
• If possible, store refrigerated or frozen items in insulated bags until they can be refrigerated.
  
  
• Bring cold foods home immediately.

Tips for storing food include:

• Always refrigerate perishable foods quickly.
  
  
• Store eggs in their original carton in the coldest part of the refrigerator (not the refrigerator door).
  
  
• Cool large volumes of food in several small containers.
  
  
• Do not store milk in the refrigerator door.
  
  
• Do not let perishable food stand at room temperature for more than two hours.
  
  
• Store meat on the bottom shelf of the refrigerator or in the back or in the freezer.
  
  
• Make sure the refrigerator is set to 40 degrees Fahrenheit (4.4 degrees Celsius) or lower. The freezer should be set to 0 degrees Fahrenheit (- 17.8 degrees Celsius).

Tips for food preparation include:

• Wash hands for at least 20 seconds with soap and warm water before and after cooking.
  
  
• Wash countertops and tables before and after cooking.
  
  
• Wash fruits and vegetables with cold running water before cutting or eating, and remove any damaged areas before eating.
  
  
• When preparing both meat and vegetables, use separate cutting boards for each.
  
  
• Defrost meats in the refrigerator or microwave and then cook immediately.
  
  
• When using a marinade for meat, it must be cooked before being placed on cooked meat.
  
  
• Cook foods to appropriate temperature. Casseroles, beef, veal, pork and lamb should be cooked to 160 degrees Fahrenheit (71.1 degrees Celsius). Poultry should be cooked to minimum internal temperatures of 165 degrees Fahrenheit (73.9 degrees Celsius), according to a recent advisory from the Food Safety and Inspection Service (FSIS). Use a meat thermometer to test temperature. Eggs should be cooked until the yolk is hard.
  
  
• Marinades used on raw meat or poultry should never be reapplied to cooked foods.
  
  
• Never place cooked meats on dishes that previously held raw meats.
  
  
• Use a clean produce brush to scrub fruit and vegetables, such as cucumbers.
  
  
• Commercial produce washed are not generally recommended.
  
  
• Dry produce with a paper towel or clean cloth to reduce and additional bacteria.

Tips for food safety while eating away from home (on picnics, car trips or sporting events) include:

• When transporting food, make sure the cooler is clean and dry before adding food.
  
  
• Keep foods well wrapped in plastic wrap or plastic containers.
  
  
• Keep foods cold with a cooler, ice, ice packs or insulated bags.
  
  
• Place meats at the bottom of the cooler to prevent drips onto other foods.
  
  
• Pack two coolers, one for food and another for beverages.
  
  
• Store the cooler in the coolest part of the car and out of the sunlight.
  
  
• Bring disposable hand wipes for cleaning if soap and water are not available.
  
  
• Do not consume foods that have been left out in hot temperatures for more than a few hours.

Tips for food safety while traveling to other countries (particularly Latin America, Asia, Africa and the Middle East) include:

• Do not drink or brush teeth with unfiltered water. Use bottled, boiled or sterilized water instead.
  
  
• Make sure the seal is intact when buying bottled water.
  
  
• Only use ice made from bottled, boiled or sterilized water.
  
  
• Eat only cooked meats, fish and vegetables.
  
  
• Eat only pasteurized dairy products and avoid soft cheese, such as Brie and cottage cheese.
  
  
• Peel and wash raw fruits with clean bottled water before eating. Wash hands before peeling and eating fruit.
  
  
• Do not buy food from street vendors.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions regarding foodborne illness:

1. Has there been a recent outbreak of foodborne illnesses in our area?
   
   
2. If there has been an outbreak, which foods should I avoid?
   
   
3. What type of foodborne illness do I have?
   
   
4. For how long will my symptoms persist? When can I expect to start to feel better?
   
   
5. Which symptoms should I immediately report to you?
   
   
6. Are there any medications I can take to relieve my symptoms?
   
   
7. Are there any medications I should avoid until I’m feeling better?
   
   
8. Which foods can I safely eat while I'm recovering from my illness?
   
   
9. Can you help me determine which contaminated food I consumed?
   
   
10. How can I avoid getting a foodborne illness in the future?
    
    
11. Can I take antibiotics as a prophylactic measure before travel?