E. coli risk factors: who is most at risk from E. coli infection

What E. coli infection is

E. coli are bacteria found in many places, including the environment, foods, water and the intestines of people and animals. Most E. coli are harmless and are part of a healthy intestinal tract, but some can make people sick with diarrhea, urinary tract infections, pneumonia, sepsis and other illnesses. This page, like CDC's E. coli pages, focuses on the kinds that cause diarrhea (CDC). For E. coli in the bladder, see our UTI risk factors guide.

People get infected after swallowing E. coli, through contaminated food or water or through contact with animals, environments or other people (CDC). MedlinePlus says one type causes travelers' diarrhea, and the worst type causes bloody diarrhea and can sometimes cause kidney failure and even death. These problems are most likely in children and in adults with weak immune systems (MedlinePlus).

Who is most at risk

CDC says anyone can get an E. coli infection, but some groups have an increased chance of infection and of getting seriously ill (CDC):

• Children younger than 5 years. Building a strong immune system takes time, so young children are more likely to get infected and more likely to get seriously ill or develop HUS.
• Adults 65 and older. With age, people are more likely to have a weaker immune system, use certain medicines and have less stomach acid. CDC adds that adults 60 or older are also more likely to get seriously ill or develop HUS.
• People with a weakened immune system, from conditions such as cancer, diabetes, liver disease, kidney disease and AIDS, or from treatments such as chemotherapy and steroids.
• International travelers, including for the kind of E. coli that causes travelers' diarrhea. Unsafe drinking water, poor sanitation and unsafe food production and handling in some countries make it easier for some kinds of E. coli to spread.

How people get infected

• Food. You can get E. coli infections by eating foods that contain the bacteria. MedlinePlus advises cooking meat well, washing fruits and vegetables and avoiding unpasteurized milk and juices (MedlinePlus).
• Water. You can also get infected by swallowing water in a swimming pool contaminated with human waste (MedlinePlus), or by drinking unsafe water (CDC).
• Animals and people. Contact with animals, their environments or other people can also spread infection (CDC).

Symptoms

Symptoms depend on the kind of E. coli. Most people have diarrhea that can be bloody or watery and stomach cramps that can be severe; some also have vomiting or a low fever (CDC). MedlinePlus also lists nausea and fatigue, and says most cases get better without treatment in 5 to 10 days (MedlinePlus).

Signs of dehydration include little or no peeing, very dark pee, being very thirsty, a dry mouth or throat, feeling dizzy or lightheaded, and crying without tears. Dehydration can happen quickly in young children; CDC says to give children with diarrhea or vomiting extra fluids, such as oral rehydration salts, and not to wait (CDC).

HUS: the serious complication

Infection with Shiga toxin-producing E. coli (STEC) can trigger hemolytic uremic syndrome (HUS), which can lead to kidney failure, permanent health problems and even death (CDC). Signs of HUS include little or no peeing, losing pink color in the cheeks and inside the lower eyelids, unexplained bruising or a rash of tiny red spots, blood in pee, feeling very tired or irritable, and decreased alertness (CDC). For long-term kidney risk in general, see our kidney disease risk factors guide.

Treatment

CDC says people with diarrhea should drink plenty of fluids, and that most people with E. coli infection recover without antibiotics. Antibiotics are sometimes used for severe intestinal illness or for people at risk for severe illness, but CDC says not to use them with STEC infection, because they can increase the chance of HUS (CDC).

Talk to your healthcare provider before taking anti-diarrheal medicine. CDC says not to use it with high fever, bloody diarrhea or STEC infection (where it can also increase the chance of HUS), and not to give anti-diarrheal medicine containing bismuth subsalicylate to children younger than 12 (CDC).

Lowering your risk

CDC says the best ways to prevent infection are keeping your hands clean, preparing food safely and drinking safe water, and that these steps are especially important for the higher-risk groups above (CDC):

• Keep your hands clean; handwashing is one of the best ways to avoid getting sick.
• Follow the four food safety steps: clean, separate, cook and chill.
• Do not drink unsafe water. When camping, hiking or traveling, use safe water for drinking, cooking and brushing your teeth.
• Do not swallow water when swimming in lakes, ponds, streams, pools or backyard kiddie pools, and do not swim if you are sick with diarrhea.
• Drink pasteurized milk and juices; look for the word "pasteurized" on milk, dairy and juice labels.

For other foodborne germs, see our Salmonella risk factors and Listeria risk factors guides.

Common questions

Is all E. coli dangerous?

No. CDC says most E. coli are harmless and help us digest food, produce vitamins and protect us from harmful germs; only some kinds make people sick (CDC).

Should I take antibiotics for E. coli?

Usually not. Most people recover without them, and CDC says not to use antibiotics with STEC infection because they can increase the chance of HUS. Ask your healthcare provider (CDC).

How long does E. coli infection last?

MedlinePlus says most cases get better without treatment in 5 to 10 days (MedlinePlus). Call your doctor for the warning signs in the box at the top of this page.