Escherichia coli (E. coli) infections are a leading type of foodborne illness. According to estimates by the Centers for Disease Control and Prevention (CDC), approximately 73,000 cases of E. coli infection occur each year in the United States. These result in an estimated 2,100 hospitalizations and about 60 deaths each year.

Most cases of E. coli infection result from consuming food or water that has been contaminated by certain strains of the E. coli bacteria. Although many strains of E. coli live harmlessly in the intestines of cattle and humans, some strains cause illness. The most common cause of E. coli infection in the United States is eating undercooked, contaminated ground beef. In developing countries, contaminated water supplies are the most common source of infection.

Common symptoms of E. coli infection include bloody diarrhea and severe abdominal pain and cramping. A diagnosis of E. coli infection begins with a physical examination, which includes a medical history and a list of foods recently consumed and recent travel. Fecal tests can identify the presence of E. coli bacteria in stool. The very young, very old and people with immune system deficiencies have the greatest risk of developing E. coli infection.

Cases of E. coli infection that are mild can be treated at home by replacing lost fluids and electrolytes, which are necessary to maintain the body’s chemical balance. Antibiotics and antidiarrheals are not used to treat E. coli infections because they may worsen symptoms. More serious cases may be treated in a hospital where patients receive fluids intravenously (through a vein), or may be treated for complications that result from E. coli infection (e.g., anemia, kidney failure).

E. coli infection may be prevented in a variety of ways. For example, ground beef should be thoroughly cooked until it reaches a temperature of 160 degrees Fahrenheit (71 degrees Celsius). Unpasteurized milk and fruit juices should be avoided. Washing hands before and after food preparation and establishing separate cutting boards for raw meat can also help prevent E. coli infection. People with diarrhea should wash their hands frequently and should avoid swimming or any other situation where they may contaminate water used by other people.

Escheria coli (E. coli) bacteria are normally present in the intestines of healthy humans and cattle. Most strains of the bacteria are harmless, although some may cause gastrointestinal illness and lead to more serious health complications outside the digestive tract.

E. coli infections occur when people come into contact with harmful strains of the bacteria – most often by consuming contaminated food or water. It is difficult to identify contaminated foods by appearance alone – most contaminated foods look and smell normal. E. coli can also be spread through contact with contaminated surfaces and by touching infected animals (e.g., petting zoos).

When bacteria enter the body through the mouth in contaminated food or water, they travel into the stomach and intestines. If enough of the bacteria are ingested and survive the gastric juices of the stomach, they attach to the intestinal wall and begin to multiply. Some bacteria proceed to release toxins that damage the intestinal lining, whereas others may actually penetrate intestinal tissue. It may be days before symptoms of infection occur. After a period of time, the bacteria leave the intestines and exit the body with feces. 

The E. coli bacteria that cause infections are passed from contact with feces to food or water. These bacteria can survive outside the body on surfaces (e.g., skin, dishes) or in water for one to three days. Contact with the bacteria spreads the disease.

E. coli infection causes diarrhea that may be bloody, as well as painful abdominal cramping. When the diarrhea is severe, it can lead to dehydration, especially in young children. Occasionally, people may become infected by E. coli, yet display no symptoms of infection.

Most cases of E. coli infection resolve without treatment. However, in a small number of cases, a serious condition called hemolytic-uremic syndrome (HUS) can occur. This may result in profuse bleeding, anemia and kidney failure. HUS tends to affect children more often than adults. In the United States, most cases of HUS are caused by E. coli infection. Although most people recover completely, some patients with HUS may develop lifelong complications, such as high blood pressure and heart failure. E. coli infections may also pass to the urinary system, where they often cause urinary tract infections.

According to estimates by the Centers for Disease Control and Prevention (CDC), there are approximately 73,000 cases of E. coli infection each year in the United States. These cases result in an estimated 2,100 hospitalizations and about 60 deaths each year.

There are hundreds of different strains of Escherichia coli (E. coli) bacteria. Many live harmlessly in the intestines of cattle and humans. However, some strains of E. coli can cause illness.  

Six strains of E. coli that cause infections have been identified. They include:

• Enterohemorrhagic E. coli (EHEC) infection. Sometimes also referred to as a Shiga toxin-producing E. coli (STEC) infection. EHEC bacteria produce a toxin that damages the lining of the large intestine. E. coli 0157:H7 is the most prominent type of EHEC. The primary symptoms of EHEC infection are grossly bloody diarrhea and severe abdominal pain and cramping. EHEC infection may lead to complications such as hemolytic-uremic syndrome (HUS) and thrombotic thrombocytopenic purpura, which involve the destruction of red blood cells, anemia and kidney failure.
  

  

  Unlike the other types of E. coli infection identified below, EHEC infection occurs primarily in developed countries, such as the United States. It is most common in northern climates (e.g., the Pacific Northwest and Canada). It affects children and adults and occurs primarily from eating undercooked, contaminated ground beef. It may also be transmitted from person to person.
  
  
• Enterotoxigenic E. coli (ETEC) infection. Bacteria produce a toxin that damages the lining of the small intestine, causing diarrhea and cramping. ETEC infection is the leading cause of childhood diarrhea in developing countries. It may be life-threatening when it involves poor health care and undernourished children. ETEC infection is also the most common cause of traveler’s diarrhea. ETEC is very common on unwashed fruits and vegetables and in drinking water in developing countries. ETEC is most commonly contracted by consuming contaminated food or water, but may also be spread by person-to-person contact.
  

  

• Enteropathogenic E. coli (EPEC) infection. Bacteria adhere to the lining of the small intestine, injuring tissue and changing the structure of microvilli (projections of cells that increase surface area in the intestines) along the intestinal wall. EPEC infection causes diarrhea that may contain mucus, but rarely any blood. Additional symptoms include vomiting, fever and life-threatening dehydration. EPEC infection primarily affects children under 2 years of age in developing countries. Unlike the other types of E. coli infection that are spread via consumption of contaminated products, EPEC infection is most commonly transmitted by person-to-person contamination – posing a serious risk to baby nurseries in developing countries.
  
  
• Enteroinvasive E. coli (EIEC) infection. Bacteria penetrate the lining of the large intestine, causing tissue inflammation and severe diarrhea. Symptoms may include blood or mucus in watery stool, tenesmus, fever and cramping. EIEC infection usually affects adults and children in developing countries. It may be confused with shigellosis, another bacterial infection that causes diarrhea.
  
  
• Enteroaggregative E. coli (EAEC) infection. Bacteria adhere to the intestinal lining in a “stacked brick” pattern. EAEC infection causes sudden and recurring bouts of diarrhea. Blood is not usually present in the stool. It usually affects travelers and children in developing countries.
  
  
• Diffusely adherent E. coli (DAEC) infection. Similar to EAEC infection except bacteria in a DAEC infection adhere to the intestinal lining in a uniform (not stacked) manner.

The most common cause of an Escherichia coli (E. coli) infection is the consumption of food or water that contains the known infectious strains of E. coli bacteria. The bacteria may be found in the intestines of cattle and humans, then passes through the digestive tract and exits the body in feces. Anything that comes into contact with harmful strains of the bacteria may become contaminated.

Food may become contaminated in a variety of ways. During slaughter, meat may come into contact with contaminated intestines. The grinding process used to produce ground beef combines meat from many different animals, possibly spreading bacteria from one animal to the entire batch of ground meat. Grinding may also spread bacteria from the meat’s surface to its interior, thoroughly mixing the bacteria into the meat.

E. coli can also be spread through contact with contaminated surfaces. The bacteria can survive outside the body and may be transferred from contaminated equipment to beef. Bacteria on a cow’s udders can pass into the raw milk produced by that cow. If milk remains unpasteurized (not sterilized by heating), E. coli in the milk may develop into an infection once ingested.

Other foods may become contaminated when they come into contact with the feces of contaminated cows, such as when it is used as fertilizer. This may include foods such as potatoes, lettuce and alfalfa sprouts. Fruits and vegetables can become contaminated if they are washed with water that is contaminated with animal manure or human sewage. Bacteria on fruit used in unpasteurized fruit juices can also lead to infection. Alfalfa sprouts are particularly prone to contamination. They grow in conditions that are ideal for E. coli growth and are typically eaten raw, which means any bacteria present on the seeds can multiply on the sprouts before being consumed.

In the kitchen, bacteria can be transferred between foods from knives, cutting boards or other utensils. Food can also become contaminated by infected humans who handle it. 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 the bacteria.

Water may become contaminated when water containing contaminated manure drains into creeks, rivers, streams and lakes. Public water systems in the United States are treated with chlorine, ultraviolet light or other methods to kill bacteria and are regularly monitored. However, they may become contaminated, as can water supplied from private wells. Swimming pools and beaches are susceptible to fecal or sewage contamination. Swallowing water while swimming, or swimming with open wounds, may allow the bacteria to enter the body and develop into an infection.

E. coli can be spread from person to person through contact with contaminated human feces and poor hygiene practices. Families and playmates of young children who have not yet been toilet trained and elderly people with fecal incontinence are especially vulnerable. This type of transmission may be responsible for E. coli outbreaks in daycare centers, hospitals and nursing homes.

The bacteria can also be spread from contact with infected animals (e.g., petting zoos).

E. coli infections tend to occur more often in the summer than in the winter. In addition, some people are more susceptible to E. coli infection, or their symptoms may be more severe than others. People who have an increased risk of developing an E. coli infection include:

• Infants and young children. The immune systems of very young people are not fully developed, making them more prone to developing E. coli infections after exposure to the bacteria. In addition, those who are not breastfed have a greater risk of contracting an E. coli infection than infants who are breastfed.
  
  
• Elderly people. As people age, their immune systems do not respond as quickly and effectively to infectious organisms – making them more susceptible to foodborne illnesses such as E. coli infections.
  
  
• People with weakened immune systems. People with conditions that weaken the body’s defenses, such as the human immunodeficiency virus (HIV) or cancer, have a greater risk of developing an E. coli infection.

The symptoms of Escherichia coli (E. coli) infection typically appear within a few days of ingesting the bacteria and last for 5 to 10 days. In most cases of E. coli infection, symptoms are mild. Some people may have an E. coli infection but display no symptoms at all.

The most common signs and symptoms of E. coli infection in the United States include:

• Bloody diarrhea
• Abdominal pain and cramping
• Nausea
• Vomiting
• Chills
• Low-grade fever (rare)

E. coli infections contracted by exposure during travel to developing countries are less common. The most common symptoms of these types of infection are diarrhea (without blood) and abdominal cramping. Symptoms generally appear within days of infection and last for less than a week.

In most cases, E. coli infections run their course in a brief period of time with no need for medications. However, a physician should be consulted if:

• The patient is elderly, younger than five years old, or has an immune system deficiency
  
  
• Nausea, vomiting or diarrhea last longer than two days
  
  
• Symptoms begin after foreign travel
  
  
• Friends or family members experience similar symptoms after eating the same food
  
  
• Liquids or medications cannot be kept in the stomach due to vomiting
  
  
• Symptoms do not improve after two days, despite drinking large amounts of fluid
  
  
• Fever is present and exceeds 101.5 degrees Fahrenheit or 38.6 degrees Celsius (taken orally)
  
  
• Nervous system symptoms, such as slurred speech, muscle weakness, double vision and difficulty swallowing (dysphagia) are present

The following signs and symptoms may require immediate medical assistance:

• Signs of shock (e.g., weak or rapid pulse, shallow breathing, shaking, chills)
  
  
• Signs of severe dehydration (e.g., dry mouth, decreased urine output, sunken eyes)
  
  
• Bloody diarrhea
  
  
• Confusion or difficulty reasoning

Escherichia coli (E. coli) infections may be diagnosed by a physician during a physical examination that includes a medical history. Current medications, foods recently eaten, locations of food consumption or purchase, and a description of symptoms may be discussed.

Many other conditions can cause symptoms (e.g., diarrhea, abdominal cramping) commonly seen with E. coli infections. Fecal tests can identify the presence of E. coli bacteria in a patient’s stool. The bacteria may be present in feces for weeks after symptoms improve. Most laboratories do not routinely test for E. coli, so it is important that physicians instruct the laboratory to specifically look for the bacteria. Anyone who experiences the sudden appearance of bloody diarrhea should be tested for the presence of E. coli.

Physicians are required to report confirmed cases of certain types of E. coli infections to public health authorities. This includes the most common type of E. coli infection in the United States, which is generally caused by consuming undercooked, contaminated beef. Local and state health departments may then investigate outbreaks (when two or more people get sick from the same source) to identify the source and prevent spread of infection. This can include questioning people recently diagnosed with an E. coli infection or people who did not get sick but ate or drank from a suspected source of infection.

Most cases of Escherichia coli (E. coli) infections resolve within 10 days, without the need for medical treatment.

The desire to treat symptoms (such as bloody diarrhea) is understandable. However, patients with an E. coli infection should avoid certain medications, because they may do more harm than good. Medications to avoid include:

• Antibiotics. These drugs have limited effectiveness in treating foodborne illnesses such as E. coli. Also, antibiotics may actually worsen symptoms for the majority of patients with E. coli infections in the United States, causing a condition known as antibiotic induced colitis. Antibiotics can increase toxin levels within the intestines and increase a patient’s risk of developing complications of infection, such as hemolytic-uremic syndrome (HUS), which causes the destruction of red blood cells and can lead to severe blood loss and kidney failure.
  
  
• Antidiarrheals. These drugs slow the rate at which food moves through the intestines. They may be harmful because they may allow the body more time to absorb toxins produced by E. coli, increasing irritation or bleeding within the intestines. Patients should avoid both prescription and over-the-counter antidiarrheals.

Treatment of E. coli infections generally focuses on supportive care for a patient’s symptoms, such as the replacement of lost fluids and electrolytes (substances necessary for normal bodily chemistry and function) to avoid dehydration as a result of diarrhea, or a diet of bland food for nausea. 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 ounces each hour).
  
  
• Avoid soft drinks, tea, coffee, fruit juice and sports drinks because they do not replace electrolytes appropriately.
  
  
• If diarrhea is severe (especially in children), drink oral rehydration solutions (fluids that contain glucose and electrolytes).

Diet tips for E. coli infection include:

• Eat foods that contain salt, such as crackers or pretzels, to replace lost sodium. Such foods are not recommended after the infection resolves.
  
  
• 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 (such as pizza) and high-fiber foods (such as bran cereal and whole grain breads) because they may worsen diarrhea.

There are currently no vaccines available to prevent Escherichia coli (E. coli) infections. Research continues in this area, with some experimental vaccines being tested in clinical trials. The use of antibiotics as a preventive measure against E. coli before traveling to developing countries should be avoided. The effectiveness of these drugs to treat E. coli infections is limited. Also, use of antibiotics may lead to the development of antibiotic-resistant strains of the bacteria.

The best ways to prevent an E. coli infection include practicing good hygiene and food safety habits. Washing hands prior to handling food or after exposure to feces is very important. This can wash bacteria away and keep it from being spread or accidentally ingested, thereby preventing infection.

Since bacteria is destroyed by cooking, make sure meat is heated to at least 160 degrees Fahrenheit (71 degrees Celsius). Ground beef may brown before reaching this temperature, so a thermometer should be used. When eating in a restaurant, order hamburger or steak that has been thoroughly cooked (not pink in the middle). If returning meat to the kitchen for more cooking, be sure to ask for a new plate and bun to prevent the possible spread of bacteria.

When cooking, be sure to keep raw meat separate from other foods. Countertops and utensils should be cleaned after coming into contact with raw meat. To avoid the spread of bacteria after cooking, do not place cooked burgers on plates that previously held the uncooked meat. Never thaw frozen meat at room temperature – use the refrigerator or the microwave.

Fruits and vegetables should be washed thoroughly before eating. People at risk for contracting E. coli infections (young children, the elderly, or people with immune system deficiencies) should avoid alfalfa sprouts, which can harbor large quantities of E. coli.

Unpasteurized products (e.g., raw milk, juice, cider) should be avoided because they have not been heated sufficiently to destroy bacteria. Only treated water should be consumed. If water is obtained from a private well, be sure to have it tested annually for bacteria. Avoid swallowing water when swimming (e.g., at the beach, lake or swimming pool) – to avoid ingesting bacteria that can result from fecal or sewage contamination of the water. 

When traveling to other countries, avoid tap water and ice and drink only bottled water, carbonated beverages or hot drinks. Fruits and vegetables should be washed in safe water or treated with iodine solutions.

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 Escherichia coli (E. coli) infection:

1. Could I have an E. coli infection?
   
   
2. Are there tests you can perform to confirm whether or not I have an E. coli infection?
   
   
3. Are my symptoms the result of something I ate? Is there a way to identify which food made me sick?
   
   
4. Is there any other way I might have contracted an E. coli infection?
   
   
5. Has there been a recent outbreak of E. coli infections in the area? If there has been an outbreak, which foods/establishments should I avoid?
   
   
6. Should members of my family be tested for E. coli? Could I have passed this on to them?
   
   
7. How long will my symptoms persist? When can I expect to start feeling better?
   
   
8. Are there any prescription or over-the-counter medications I can take to relieve my symptoms? Are there any I should avoid?
   
   
9. Which foods can I safely eat while I'm recovering from my infection? Are there specific foods or beverages I should avoid?
   
   
10. What changes in my symptoms do you want me to report to you?
    
    
11. Am I at risk of developing complications from an E. coli infection?
    
    
12. What can I do to avoid this type of infection in the future?