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 or 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.