What is an E. coli infection?
E. coli ( Escherichia coli) is the name of a germ, or bacterium, that lives in the digestive tracts of humans and animals.
There are many types of E. coli, and most of them are harmless. But some can cause bloody diarrhea. Some strains of E. coli bacteria may also cause severe anemia or kidney failure, which can lead to death.
Other strains of E. coli can cause urinary tract infections or other infections.
What causes an E. coli intestinal infection?
You get an E. coli infection by coming into contact with the feces, or stool, of humans or animals. This can happen when you drink water or eat food that has been contaminated by feces.
E. coli in food
E. coli can get into meat during processing. If the infected meat is not cooked to 160°F (71°C), the bacteria can survive and infect you when you eat the meat. This is the most common way people in the United States become infected with E. coli. Any food that has been in contact with raw meat can also become infected.
Other foods that can be infected with E. coli include:
- Raw milk or dairy products. Bacteria can spread from a cow's udders to its milk. Check the labels on dairy products to make sure they contain the word "pasteurized." This means the food has been heated to destroy bacteria.
- Raw fruits and vegetables, such as lettuce, alfalfa sprouts, or unpasteurized apple cider or other unpasteurized juices that have come in contact with infected animal feces.
E. coli in water
Human or animal feces infected with E. coli sometimes get into lakes, pools, and water supplies. People can become infected when a contaminated city or town water supply has not been properly treated with chlorine or when people accidentally swallow contaminated water while swimming in a lake, pool, or irrigation canal.
E. coli from person-to-person contact
The bacteria can also spread from one person to another, usually when an infected person does not wash his or her hands well after a bowel movement. E. coli can spread from an infected person's hands to other people or to objects.
What are the symptoms?
The main symptoms of an E. coli intestinal infection are:
- Bloody diarrhea.
- Stomach cramps.
- Nausea and vomiting.
Some people do not notice any symptoms. Children are more likely than adults to have symptoms. Symptoms usually start 3 or 4 days after you come in contact with the E. coli.
Most people get better in about a week. They often don't see a doctor and don't know that E. coli caused their problems.
When E. coli causes serious problems with the blood or kidneys, symptoms include:
- Pale skin.
- A fever.
- Passing only small amounts of urine.
How is an E. coli intestinal infection diagnosed?
Your doctor may suspect that you have an E. coli infection after he or she asks you questions and does an exam. Your stool will probably be tested for E. coli.
How is it treated?
E. coli infection usually goes away on its own. Your main treatment is to make yourself comfortable and drink sips of water. Diarrhea causes the body to lose more water than usual. This can lead to dehydration, which is especially dangerous for babies and older adults. Taking frequent, small sips of water will help prevent dehydration.
If you have bloody diarrhea that may be from an E. coli infection, do not take diarrhea medicine or antibiotics. These medicines can slow down the digestion process, allowing more time for your body to absorb the poisons made by the E. coli. Call your doctor instead.
In some people, E. coli infection causes serious problems with the blood and kidneys. These people may need blood transfusions or dialysis. Dialysis is a treatment that helps filter waste products from the blood when the kidneys aren't working right.
How do you prevent an E. coli intestinal infection?
Food and water that are infected with E. coli germs look and smell normal. But there are some things you can do to prevent infection:
- Cook ground beef to at least 160°F (71°C).
- In the kitchen, wash your hands with hot, soapy water often, especially after you touch raw meat.
- Wash any tools or kitchen surfaces that have touched raw meat.
- Use only pasteurized milk, dairy, and juice products.
- Use only treated, or chlorinated, drinking water.
- When you travel to countries that may have unsafe drinking water, don't use ice or drink tap water. Avoid raw fruits and vegetables, except those with skin that you peel yourself.
- Wash your hands often, and always wash them after you use the bathroom or change diapers.
Children are more likely than adults to develop symptoms of an E. coli infection. Most people with the infection will have:
- Severe stomach cramps and stomach tenderness.
- Diarrhea, watery at first, but often becoming very bloody.
- Nausea and vomiting.
Some people who are infected with the bacteria do not notice any symptoms. They may spread the bacteria to others without knowing it.
There are many conditions with symptoms similar to those of E. coli intestinal infection. Diagnosis of E. coli infection can be complicated by the fact that most bacterial infections that cause diarrhea are accompanied by a high fever. If you have no fever or only a mild fever, your doctor may suspect that something other than bacteria is causing your symptoms.
Bloody diarrhea is common in confirmed cases of E. coli intestinal infection, but the bacteria also should be considered a possible cause of non-bloody diarrhea.
Symptoms of E. coli infection usually end in about a week with no further problems. But severe blood and kidney problems may occur within 2 weeks after the onset of diarrhea. These problems can cause kidney failure and sometimes long-term disability or death in some children and older adults.
Exams and Tests
The medical evaluation for diarrhea that may be caused by disease-causing E. coli bacteria usually starts with a physical examination and a medical history.
During the medical history, your doctor will ask questions about your symptoms, such as:
- When did diarrhea begin, how long has it lasted, and how frequent are bowel movements?
- Is there blood in the diarrhea? If so, how much?
- Have you had chills or a fever?
- Have you had any abdominal cramps, nausea, or vomiting?
- Do you feel tired or irritable?
- Have you fainted or felt lightheaded?
Infection with E. coli is easily mistaken for other conditions with similar symptoms, such as other infectious diseases.
A doctor may suspect you have E. coli infection if you have been exposed to the bacteria. During the medical history, your doctor may ask if you have:
- Been in a day care center, school, nursing home, or other adult care institution.
- Eaten recently at a restaurant.
- Consumed any undercooked meat or unpasteurized milk, dairy products, or juice.
- Had contact with anyone with recent or ongoing diarrhea.
- Traveled recently.
- Used antibiotics recently.
During the physical examination, a doctor will usually:
- Take your temperature.
- Take your blood pressure and determine your pulse rate.
- Look at your skin color to see whether you are unusually pale.
- Check your stomach for tenderness.
- Perform a rectal exam to find out whether you have blood in your stool.
Doctors who suspect E. coli infection will order a type of stool culture that detects strains of E. coli. Because the bacteria can leave the body in only a few days, the sample should be obtained as soon as possible after symptoms appear.
Other tests are sometimes used when the diagnosis is unclear, but these are not yet widely available.
If a child or older adult is diagnosed with E. coli infection, he or she may be watched for development of severe blood or kidney problems. Monitoring requires blood and urine tests to measure essential elements of blood and body fluids.
Treatment of infection with disease-causing E. coli bacteria involves managing complications—mainly dehydration caused by diarrhea.
If you develop symptoms of severe blood or kidney problems, such as anemia or kidney failure, your treatment may include:
- Careful regulation of fluids and essential minerals.
- Dialysis, to filter waste products from your blood. Some people with kidney failure caused by E. coli infection require dialysis.
- Blood transfusion, to treat anemia by giving you additional oxygen-rich red blood cells.
Medicines to avoid
Most people recover from E. coli infections in 5 to 10 days without the need for medicine. Antibiotics are not recommended. Tell your doctor if you think you may have E. coli infection and are taking antibiotics.
Nonprescription or prescription diarrhea medicines usually are not used to treat E. coli infection. Many antidiarrheal products slow the rate at which food and waste products move through the intestines. This may allow more time for the body to absorb the poisons produced by the bacteria, increasing the risk of complications such as severe blood and kidney problems.
Avoid these nonprescription products if you have or suspect you have an E. coli infection:
- Loperamide products. These include Imodium, Maalox, and other antidiarrheal products. Note: Only those products that list loperamide in their ingredients should be avoided.
- Products containing salicylates. These include Pepto-Bismol and similar bismuth-based antidiarrheal products, aspirin, and ibuprofen (such as Advil). Salicylates can increase bleeding from the intestines. Also, salicylates are associated with Reye syndrome, a rare but serious illness in children.
Prescription diarrhea medicines may be harmful when given to a person with E. coli infection. A doctor may prescribe one of these medicines if he or she does not know that E. coli caused the diarrhea. Be sure to discuss your symptoms with your doctor. Sharing information is important to get the proper diagnosis of your condition.
Avoid these prescription medicines if you have or think you may have an E. coli infection:
- Difenoxin with atropine (Motofen)
- Diphenoxylate with atropine (Lomotil)
- Loperamide (prescription-strength Imodium)
Home treatment of infection with disease-causing E. coli bacteria consists of keeping yourself comfortable and preventing the spread of the bacteria. If you aren't infected, take steps to prevent infection.
If you think that you or someone in your care may be infected with E. coli, contact a doctor immediately. Do not treat diarrhea symptoms with any nonprescription or prescription medicines.
Home treatment for diarrhea or bloody diarrhea caused by E. coli infection
- Do not use nonprescription antidiarrheal products if you have bloody or non-bloody diarrhea that you suspect may be caused by E. coli infection. These products include Imodium and Maalox Anti-Diarrheal. Do not take other medicines that you have left over from a previous illness.
- Take frequent, small sips of water or a rehydration drink to replace lost fluids and help prevent dehydration. Because dehydration can be more dangerous in babies, call your doctor if you think your baby may be dehydrated. Your stomach cannot handle too much fluid at one time. Seek medical care if you develop signs of moderate dehydration, which include:
- Dry appearance inside the mouth.
- Eyes that don't tear.
- Low output of urine.
Especially in children and adults age 65 and older, watch for symptoms of severe blood and kidney problems, such as fever, weakness, pale skin, or passing small amounts of urine. If any of these symptoms develop, see a doctor immediately.
Tips for protecting yourself against E. coli infection from contaminated food and water
- Cook ground beef to a temperature of at least 160°F (71°C). Ground beef should be cooked until all pink color is gone, but don't rely only on color. Check the temperature with a meat thermometer. Cut open restaurant and home-cooked hamburgers to ensure that they have been completely cooked. The juices should be clear or yellowish, with no trace of pink. Never eat raw or undercooked ground beef.
- When preparing food:
- Wash your hands often with hot, soapy water, especially after handling raw meat.
- Always wash cooking tools, cutting boards, dishes, counter tops, and utensils with hot, soapy water immediately after they have come into contact with raw meat. Do not put cooked meat back onto a plate that has held raw meat unless the plate has been thoroughly washed with soap and water and dried.
- Use separate cutting boards for raw meat and for other food items.
- Keep raw meat, poultry, and seafood separate from vegetables, fruits, breads, and other foods that have already been prepared for eating.
- Use only pasteurized milk, dairy, and juice products. Check product labels for the word "pasteurized." Juice made from concentrate is the same as pasteurized.
- Use only treated (chlorinated) drinking water.
- Travelers to countries where the water supply may not be safe should be especially careful not to put ice in their drinks or drink tap water. All water consumed should be boiled or bottled. Eat meals when they are hot. Avoid raw fruits and vegetables, except those with skin that you peel yourself.
Tips for preventing person-to-person spread of E. coli bacteria
- Wash your hands often, and always wash them after bowel movements or changing diapers. If your home has more than one bathroom, restrict the infected person to the use of one bathroom only.
- Dispose of soiled diapers and stools carefully. If the infection is suspected in a young child, use disposable diapers instead of cloth diapers until the illness has passed.
- Adults should make sure that children who have diarrhea wash their hands thoroughly after using the bathroom. Children infected with E. coli should avoid contact with other children, particularly during swimming.
- Wash handles on toilets and sinks with an antibacterial cleaner.
- People who have been diagnosed with E. coli infection should not handle food or work in a day care center or other institution until they have tested negative for the bacteria in two stool samples. If you have taken any antibiotic, the stool sample should be taken at least 48 hours after you took the last dose.
- Chlorinate water in swimming pools and hot tubs.
Other Works Consulted
- American Academy of Pediatrics (2015). Escherichia coli diarrhea (including hemolytic-uremic syndrome). In DW Kimberlin et al., eds., Red Book: 2015 Report of the Committee on Infectious Diseases, 30th ed., pp. 343–347. Elk Grove Village, IL: American Academy of Pediatrics.
- Procop GW, Cockerill F III (2001). Enteritis caused by Escherichia coli and Shigella and Salmonella species. In WR Wilson et al., eds., Current Diagnosis and Treatment in Infectious Diseases, pp. 548–556. New York: McGraw-Hill.
Current as of: June 9, 2019
Author: Healthwise Staff
E. Gregory Thompson MD - Internal Medicine
Kathleen Romito MD - Family Medicine
Adam Husney MD - Family Medicine
Elizabeth T. Russo MD - Internal Medicine
W. David Colby IV MSc, MD, FRCPC - Infectious Disease