Escherichia coli (E. coli) | Infectious Diseases

Infectious Diseases

E. coli

An E. coli infection can be much more serious than regular food poisoning. UC Davis Health is at the forefront of E. coli research and care.

Medically reviewed by Dean Blumberg, M.D. on Nov. 08, 2023.

Person's hands cutting raw chicken on a cutting board.

What Is E. coli Infection?

Escherichia coli (E. coli) is bacteria that live in your intestines and helps with food digestion. These bacteria can also live in the intestines of some animals. Most types of E. coli are harmless, but some types can cause intestinal illness.

Intestinal illness most commonly occurs due to a type of E. coli that makes a toxin (Shiga). Shiga toxin damages your small intestine lining.

At the Division of Infectious Diseases, we offer the latest care for E. coli infection. We use the most up-to-date research and tools to prevent, diagnose and treat this infectious disease.


Symptoms of E. coli Infection

E. coli symptoms usually start 3 to 4 days after eating or drinking a substance containing the bacteria. But symptoms can also begin from 1 to 10 days after you’re exposed.

Common Symptoms

If you have an E. coli infection, you may experience:

  • Abdominal cramps
  • Diarrhea, which is often bloody
  • Fatigue
  • Fever of usually less than 101°F
  • Nausea and vomiting

Emergency Symptoms

About 5-10% of people with an E. coli infection develop a life-threatening condition called hemolytic uremic syndrome (HUS). HUS symptoms show up about 7 days after your first symptoms and may include:

  • Decreased urination
  • Extreme fatigue
  • Kidney failure
  • Increased heart rate
  • Loss of pink cheek color
  • Lightheadedness and confusion
  • Seizures

Causes of E. coli Infection

You can become infected with E. coli by eating or drinking contaminated food or liquids, or from contact with other infected people or animals. The most common causes of E. coli infection include:

Contaminated Food

Eating contaminated food is the most common way to get an E. coli infection. Foods that may contain E. coli include ground beef (especially undercooked meat); unpasteurized milk or juices; vegetables, fruit and cheeses made from raw milk.

Contaminated Water

Swallowing water contaminated with E. coli from animals or humans can cause an infection. You may find contaminated water in lakes, rivers, streams, wells and local water supplies.

Contact With Others

You can pass along E. coli bacteria on your hands if you touch feces after having a bowel movement, change a diaper or touch the hands of someone who is infected. You may also become infected at a petting zoo or from farm animals.


E. coli Risk Factors

The chances of getting an E. coli infection or more complications may be higher if you have one or more of these risk factors:


Children under 5 and adults over 65 are at greater risk of illness and complications from an E. coli infection.

Consuming Specific Foods

Eating undercooked meats, unpasteurized milk or juice or raw milk cheeses can increase your risk.

Lower Stomach Acid

Taking a medication to decrease stomach acid may raise your risk of an E. coli infection.

Weaker Immune System

Having a weaker immune system, from conditions such as diabetes, HIV/AIDS, urinary tract infections (UTIs), chemotherapy or medications after organ transplants, may increase E. coli infection risk.


Diagnosing an E. coli Infection

To diagnose an E. coli infection, we send a sample of your stool (poop) to a lab. They can test the sample for E. coli bacteria.

E. coli Treatments at UC Davis Health

Most E. coli infections go away on their own in about 5 to 7 days. We recommend drinking plenty of fluids and resting to help you feel better. If you have hemolytic uremic syndrome (HUS), we may treat you in the hospital with procedures such as:

Blood Transfusions

Transfusion of platelets can help your blood clot and red blood cells can help reduce anemia symptoms related to HUS.

Intravenous Fluids

You may get intravenous (IV) fluids through a vein to help replace lost fluids.

Kidney Dialysis

We may use kidney dialysis to remove waste and excess fluid from your blood if your kidneys stop working properly.


We suggest medications to lower your blood pressure if HUS causes kidney damage.


Preventing E. coli Infection

There are certain steps you can take to reduce your risk of an E. coli infection:

Avoid Unpasteurized Products

Not drinking unpasteurized milk or juice can help prevent E. coli infection.

Don’t Swallow Water From Outdoor Sources

Avoid swallowing water in lakes, ponds, streams and swimming pools.

Cook Meats Thoroughly

Cook beef steaks and roasts to at least 145°F and ground beef and pork to at least 160°F.

Prevent Cross-Contamination

Wash cutting boards, counters and utensils before and after they contact raw meat.

Rinse Fruits and Vegetables

Always rinse fruits and vegetables thoroughly to get rid of any bacteria.

Wash Your Hands

Wash your hands before or after eating food, using the bathroom, changing a diaper and coming into contact with animals.

“E. coli (Escherichia coli) – Prevention,” Centers for Disease Control and Prevention (CDC), 

Hemolytic uremic syndrome (HUS) may affect up to

10%Of people with Shiga toxin-producing E. coli (STEC) infection

Source: World Health Organization: E. coli

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