What is Food poisoning?

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, food poisoning 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 food poisoning 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 food poisoning. 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.

How is it diagnosed?

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 food poisoning (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.

How is food poisoning treated?

Treatment for food poisoning 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 food poisoning (e.g., shigellosis) that respond to antibiotic treatment, and antibiotics can worsen some types of foodborne illness.

Medications

Activity

Bed rest during acute phase. Convenient access to a bathroom or bedpan is important.

Diet

• Liquid diet using special oral glucose-electrolyte preparations, clear broth, or bouillon. Use salt and sugar in liquids to replace what was lost. Try to take small sips even if vomiting continues. This will help with volume replacement and oral rehydration.
• Progress to soft, bland diet. Return to regular diet gradually.

What might complicate it?

The infection may be complicated if the infection develops into chronic disease with fluid accumulation and lymphatic vessel blockage or rupture. Chronic lung damage may result from worm invasion of the lungs. Relapses may occur. Antifilarial drug treatment of chronic disease may lead to systemic allergic reactions to the dying worms. Dead adult worms may calcify and create abscesses in the tissues.

Predicted outcome

Complications can include hemolytic uremic syndrome, Guillain Barr' syndrome, Reiter syndrome, severe dehydration, respiratory failure, neurological problems, abscess formation, infection in the blood (sepsis), and pneumonia.

Alternatives

Conditions with similar symptoms include heavy metal poison, endocrine disorders, and congenital or acquired enzyme deficiency.

Appropriate specialists

Internist, gastroenterologist and infectious disease specialist.

Last updated 1 July 2015