Symptoms

Children are more likely than adults to develop symptoms of E. coli O157:H7 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 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 infection, but the bacteria also should be considered a possible cause of non-bloody diarrhea.

For more information on when to call a doctor about non-bloody diarrhea, see the topic:

• Diarrhea, Age 12 and Older
• Diarrhea, Age 11 and Younger

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 E. coli O157:H7 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.