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E. coli Infections


There are many different types or strains of Escherichia coli (E. coli) bacteria. Most E. coli strains are harmless and live normally in the intestines of people and animals. However, some strains of E. coli can make you sick with diarrhea, urinary tract infection, or other illnesses.


E. coli 0157

E. coli of the strain number O157, also known as E. coli O157:H7, are one type of E. coli that cause illness in people.  Food and liquids become contaminated with E. coli O157:H7 by coming into contact with the stool of an infected person or animal.  A person can become infected by eating food or drinking liquids that are contaminated.  This is known as "fecal-oral" mode of transmission.  Food handlers such as cooks and servers who are themselves infected, can pass the infection to customers at markets and restaurants.

There have been many outbreaks of E. coli O157:H7 disease in the USA.  Meat or dairy products from infected animals, particularly cows, can become contaminated during processing.  Outbreaks have been traced to contaminated ground beef or unpasteurized dairy products.   Fruits and vegetables can also become contaminated by stool from infected grazing animals.  Outbreaks have been traced to raw sprouts, leafy green vegetables such as lettuce or spinach, and unpasteurized fruit juices.

Symptoms of E. coli O157:H7 appear from 1-10 days (but usually within 2-4 days) after consuming contaminated food or drink.  The illness can range from mild to quite severe.  Typical symptoms include belly cramps, diarrhea, and bloody diarrhea.   Most people with E. coli O157:H7 infection recover completely within a 5-10 days.  A small percentage (about 8 out of 100) develop hemolytic-uremic syndrome (HUS).  Children under age five, and elderly persons, have the highest risk.  In hemolytic-uremic syndrome, red blood cells break down and the kidneys fail.  This is a serious complication of E. coli O157:H7 infection, requiring hospitalization and often kidney dialysis. 

E. coli O157:H7 is diagnosed by a stool test.  Your doctor can order a "stool culture" to look for infectious E. coli as well as other causes of bloody diarrhea.

Treatment for E. coli O157:H7 is supportive, meaning that no specific drug or antibiotic is known to be helpful.  Drinking plenty of fluids is recommended to prevent dehydration if there is a lot of diarrhea.  Fortunately, most cases recover completely on their own, without any specific treatment.  Antibiotics are not recommended for E. coli O157:H7 infections, as they may increase the chance of getting HUS.

People can take the following steps to help prevent E. coli O157:H7 infections.

  • Cook all ground beef and hamburger thoroughly. Ground beef should be cooked until a thermometer inserted into the thickest part of the patty reads at least 160 degrees F on a digital thermometer or until the patty is no longer pink inside.
  • Drink only pasteurized milk, juice, or cider.  Avoid cheeses and dairy products made from "raw" or unpasteurized milk.
  • Wash fruits and vegetables thoroughly, especially those that will not be cooked. Raw sprouts can carry E. coliO157 and therefore should be avoided, especially by children under five years of age, immunocompromised persons, and the elderly, all of whom are at risk of serious disease if infection occurs.
  • Wash your hands thoroughly with soap and water after using the bathroom, changing diapers, preparing or eating food, or having contact with animals.
  • Do not prepare food for others if you are sick, especially if you are sick with diarrhea or bloody diarrhea.
  • Prevent cross-contamination in the kitchen by thoroughly washing hands, counters, cutting boards, and utensils after they touch raw meat, fruits, or vegetables.



E. coli O157 cause disease by producing a toxin that affects the intestines.  This toxin is known as Shiga toxin.  The E. coli bacteria capable of producing this toxin are known as Shiga toxin-producing E. coli (STEC).  E. coli O157 are just one strain of STEC and are responsible for about one-third of the STEC infections nationwide.   Other STEC strains, known as non-O157 strains, include O26, O45, O111, O121, and O145.  According to an estimate by the Centers for Disease Control & Prevention (CDC), STEC cause approximately 100,000 illnesses, 3,000 hospitalizations, and 90 deaths per year in the USA.


For more information on E. coli 0157 and STEC:

SFDPH Frequently Asked Questions about E. coli

California Department of Public Health Fact Sheet

Centers for Disease Control web page, laboratory recommendations, and other publications

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