E. coli Infection: What It Is, How You Catch It, and When to Seek Care
Updated: 22 hours ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: November 2026
Quick Answer
An E. coli infection is any illness caused by strains of Escherichia coli bacteria, most often gastroenteritis or a urinary tract infection, usually spread through contaminated food, water or surfaces [1]. Most cases improve within two days to two weeks [1], but STEC must not be treated with antibiotics or anti-diarrheals [1] [3]. Go to the ER for bloody diarrhea or confusion [1].
What the research says
Antibiotics were linked to a higher risk of kidney-damaging HUS in E. coli O157 infection. A meta-analysis of 23 studies including 17,975 patients found that treatment with any antibiotic was associated with a higher risk of hemolytic uremic syndrome (OR 1.47, 95% CI 1.03–2.09), with β-lactams carrying the highest risk (OR 2.37, 95% CI 1.79–3.15), while fosfomycin was associated with a lower incidence (OR 0.56, 95% CI 0.40–0.77); the authors concluded that antibiotic therapy slightly increased the risk of progression to HUS (PubMed: Sevilla et al., Eur J Clin Microbiol Infect Dis, 2025 [2]).
The antibiotic–HUS link becomes clearer when only the most reliable studies are counted. In an earlier meta-analysis of 17 reports and 1,896 patients with STEC infection, the pooled odds ratio for HUS after antibiotics was 1.33 (95% CI 0.89–1.99) across all studies but rose to 2.24 (95% CI 1.45–3.46) when only low-risk-of-bias studies using accepted HUS definitions were analyzed, leading the authors to advise against antibiotics in STEC infection (PubMed: Freedman et al., Clin Infect Dis, 2016 [3]).
No treatment has been proven to prevent HUS once STEC infection has started. A Cochrane review of four randomized trials (536 participants) testing antibiotics, bovine colostrum, a Shiga toxin binding agent and a monoclonal antibody could draw no firm conclusions about benefits or harms because of the small number and size of the studies; for trimethoprim-sulfamethoxazole (47 participants) the effect on HUS was uncertain (RR 0.57, 95% CI 0.11–2.81, very low-certainty evidence) (PubMed: Imdad et al., Cochrane Database Syst Rev, 2025 [4]).
What Is E. coli?
Escherichia coli (E. coli) is a group of bacteria that normally lives in the gut (gastrointestinal/GI tract) of healthy people and animals [1]. The type that lives in your GI tract usually doesn't hurt you — it even helps you digest your food. But under certain circumstances, many strains (types) of E. coli can make you sick. Many of the strains that cause infection can adhere (stick) to your cells and release toxins [1].
An E. coli infection is any illness you get from strains of E. coli bacteria. There are harmful strains that cause watery diarrhea, stomach pain, and other digestive symptoms (gastroenteritis) if you accidentally ingest them. These are sometimes called diarrheagenic E. coli, and they're often what people mean when they talk about E. coli infections. But the E. coli that usually lives in your gut can also get into places it isn't supposed to be — like your urinary tract — and cause an infection there.
Many strains of E. coli cause mild infections. But some strains, like those that produce Shiga toxin, can cause serious illness, including kidney damage [1].
Quick fact | Detail |
What it is | A group of bacteria; most strains live harmlessly in the human gut |
When it causes illness | When harmful strains are ingested, or normal gut E. coli reaches the wrong body site |
Most dangerous strain | Shiga toxin-producing E. coli (STEC); subtype O157:H7 is most likely to cause severe illness |
How common | About 265,000 STEC infections each year in the U.S.; STEC is the most common cause of E. coli outbreaks and serious illness |
Usual duration | Two days to two weeks; STEC infections usually last five to seven days |
Contagious? | Yes — spread person to person through fecal contact, not by sneezing or coughing |
What are the signs and symptoms of an E. coli infection?
Symptoms of an E. coli infection depend on where in the body the bacteria are causing trouble. The two most common forms are gastrointestinal infection (gastroenteritis) and urinary tract infection (UTI).
Symptoms of E. coli in your digestive tract
Symptoms of E. coli gastroenteritis include diarrhea — often watery and sometimes bloody — stomach pains and cramps, loss of appetite, and low fever [1]. Watery diarrhea is usually the first symptom of an E. coli infection in your GI tract [1].
Symptoms of E. coli in your urinary tract
If E. coli infects parts of your urinary tract, you might have abdominal or pelvic pain, a pain or burning sensation when you pee, an urgent need to pee frequently, and cloudy, foul-smelling pee [1].
Body site | What it's called | Typical symptoms |
Gastrointestinal tract | Gastroenteritis | Watery diarrhea (sometimes bloody), stomach pains and cramps, loss of appetite, low fever, nausea, vomiting, fatigue |
Urinary tract | UTI | Abdominal or pelvic pain, burning when peeing, urgent and frequent need to pee, cloudy foul-smelling urine |
Bloodstream | Septicemia | Fever, chills, low blood pressure, organ dysfunction (sepsis reaction) |
Prostate | Prostatitis | Pelvic pain, urinary symptoms |
Female reproductive tract | Pelvic inflammatory disease (PID) | Pelvic pain, abnormal discharge |
Gallbladder | Cholecystitis | Right upper abdominal pain, fever |
Skin/wounds | Wound infection | Redness, swelling, pus |
Lungs | Pneumonia (rare) | Cough, fever, breathing difficulty |
Brain/spinal fluid | Meningitis (rare) | Fever, stiff neck, confusion — especially in newborns (E. coli K1 strain) |
How soon do symptoms start?
You usually develop symptoms of an STEC infection within three to five days after drinking or eating foods contaminated with this E. coli bacteria [1]. Other strains can make you sick within hours. Sometimes, symptoms start up to 10 days after exposure [1]. Other guidance puts the usual start at 3 to 4 days after exposure, with symptoms sometimes beginning as early as one day or more than a week later [5].
What Causes E. coli Infections?
Many strains of E. coli can cause diarrheagenic infections in your GI tract. Most cause similar symptoms, like watery diarrhea, but some are more serious than others. Scientists categorize them by how they attach to your cells and the types of toxins they release.
The six types of diarrheagenic E. coli
Type | What it does |
Shiga toxin-producing E. coli (STEC) | Releases Shiga toxin (the same toxin as Shigella bacteria); damages cells; can cause bloody diarrhea and kidney-damaging HUS; most likely to cause outbreaks from contaminated food |
Enterotoxigenic E. coli (ETEC) | Causes traveler's diarrhea; symptoms start quickly, sometimes within hours; common in warm climates |
Enteropathogenic E. coli (EPEC) | Attaches to intestinal cells and causes diarrhea, especially in children |
Enteroaggregative E. coli (EAEC) | Clusters on the intestinal lining and causes watery diarrhea |
Enteroinvasive E. coli (EIEC) | Invades the intestinal wall like Shigella; can cause bloody diarrhea |
Diffusely adherent E. coli (DAEC) | Spreads across intestinal cells and can cause diarrhea |
Two other notable types deserve mention. Uropathogenic E. coli (UPEC) can cause UTIs, and E. coli K1 can cause meningitis in newborns [1].
What are Shiga toxin-producing E. coli (STEC)?
STEC is a strain of E. coli that releases a toxin (Shiga toxin) that damages your cells. These are the same toxins released by Shigella bacteria [1]. STEC is known for causing severe outbreaks of E. coli (where many people get sick), often from contaminated food.
STEC is also called enterohemorrhagic E. coli (EHEC) because it can lead to bleeding in your intestines, causing bloody diarrhea (hemorrhagic colitis). About 5% to 10% of people with STEC develop hemolytic uremic syndrome (HUS), a condition that causes blood clots and damages your kidneys [1]. The subtype E. coli O157:H7 is the most likely to cause severe illness [1].
How do you get E. coli?
Most diarrheagenic E. coli strains spread through fecal-oral transmission [1]. This happens when bacteria from poop that's too small to see make their way into your mouth and digestive tract. Some forms, like STEC, can also transmit through undercooked meat and unpasteurized beverages [1].
Transmission route | How it happens |
Contaminated food | Undercooked meat; raw fruits and veggies that aren't washed well enough |
Unpasteurized beverages | Raw milk, cider, or juice — and foods made from them, like cheese or ice cream |
Contaminated water | Water from lakes, streams, and rivers; swimming pools; drinking water that isn't sanitized — or getting it in your mouth while swimming |
Touching poop or contaminated surfaces | Changing diapers, wiping after a bowel movement, touching petting zoo or farm animals, or sharing objects with someone who has an infection — then swallowing bacteria transferred from hands to mouth |
Poor wiping technique | Moving E. coli from poop to the urinary tract, causing a UTI |
During birth | Babies sometimes get E. coli infections during delivery |
Ground beef carries a higher risk than whole cuts because it combines meat from more than one animal [5]. E. coli on a cow's udder or on milking machines can get into raw milk [5]. Runoff from cattle farms can contaminate the fields where produce grows, and spinach and lettuce are especially likely to carry the bacteria [5]. Public water systems use chlorine, ultraviolet light or ozone to kill E. coli, but some outbreaks have still been linked to contaminated city water [5].
Is E. coli contagious? Yes, E. coli can be contagious (spread from person to person). While you don't get it from sneezing or coughing, you can get it from caring for someone with an E. coli infection, especially if you come in contact with their poop. You can also get it from objects, surfaces, or food someone with an E. coli infection has touched if they don't wash their hands well enough [1].
Who's at greatest risk?
Anyone who comes into contact with a disease-causing strain of E. coli can get infected. People who are at greatest risk include newborns and young children, people over the age of 65, people who have weakened immune systems (for example, those with HIV or cancer or who take immunosuppressive medications), people with diabetes, and people with ulcerative colitis [1]. Taking medicines that reduce stomach acid, such as esomeprazole, pantoprazole, lansoprazole and omeprazole, is also a risk factor [5].
Complications
E. coli sometimes causes life-threatening complications, including hemolytic uremic syndrome (HUS), sepsis (a serious reaction to an infection in your bloodstream), and malnutrition or delayed growth in children with chronic diarrhea who can't absorb the nutrients they need to grow [1]. Young children and older adults are at higher risk of HUS [5]. If HUS develops, hospital treatment may include fluids through a vein, blood transfusions and kidney dialysis [6].
Complication | What it involves |
Hemolytic uremic syndrome (HUS) | Blood clots and kidney damage; develops in about 5%–10% of people with STEC |
Sepsis | A serious body-wide reaction to a bloodstream infection; the most common cause of death in E. coli infections |
Malnutrition / delayed growth | Chronic diarrhea in children can prevent nutrient absorption needed for growth |
How Is an E. coli Infection Diagnosed?
How your provider diagnoses E. coli depends on what your symptoms are. If you have diarrhea or other digestive symptoms, your provider will test a stool (poop) sample for E. coli. If you have other symptoms, they might test your urine (pee), blood, or cerebrospinal fluid (CSF) [1].
Test | When it's used |
Stool test | Diarrhea or other digestive symptoms |
Urinalysis or urine culture | Suspected UTI symptoms |
Blood culture | Suspected bloodstream infection (sepsis) |
Spinal tap (lumbar puncture) | Suspected meningitis, especially in newborns |
How is an E. coli infection treated, and what is the STEC warning?
You often don't need to treat E. coli infections that cause digestive symptoms. Healthcare providers specifically don't treat STEC with antibiotics or antidiarrheal medicines. These medications can increase your risk of HUS if you have STEC [1] [2] [3]. Instead, they'll monitor your condition and give you fluids to prevent dehydration if needed [1].
But if you have another type of E. coli infection — like a UTI, meningitis, or sepsis — or if your symptoms are severe, your provider will treat you with antibiotics [1].
Situation | Treatment approach |
Mild gastroenteritis | Often no treatment needed; fluids; recovery in about a week |
STEC infection (including O157:H7) | No antibiotics, no anti-diarrheals (bismuth subsalicylate/Pepto-Bismol/Kaopectate or loperamide/Imodium) — they raise HUS risk; monitoring, fluids, possible hospitalization and isolation |
UTI, meningitis, sepsis, or severe symptoms | Antibiotics |
Common antibiotics used | Trimethoprim/sulfamethoxazole (TMP/SMX), ciprofloxacin, rifaximin, nitrofurantoin |
Self-care while recovering
Don't eat or drink anything that makes diarrhea worse, like caffeine or alcohol. Drink plenty of fluids to stay hydrated. If a provider has diagnosed you with STEC (especially E. coli O157:H7), don't take anti-diarrheal medications like bismuth subsalicylate (Pepto-Bismol, Kaopectate) or loperamide (Imodium). These medications can increase your risk of HUS [1]. Antidiarrheal medicine also slows the digestive system and keeps the body from getting rid of the toxins [6]. Water, broth and rehydration solutions are good choices, while apple and pear juices, dairy products and fatty, high-fiber, salty or spicy foods can make symptoms worse [6]. You can go back to your usual diet once you start to feel better [6].
What is the outlook for an E. coli infection?
E. coli infections can cause everything from brief bouts of diarrhea to life-threatening illness. Most people recover on their own or with antibiotic treatment. Providers usually don't treat STEC infections, but you might need supportive care, like supplemental fluids or nutrition. You might also be hospitalized and isolated to keep STEC from spreading [1].
Depending on the type of E. coli infection you have, your symptoms can last from two days to two weeks [1]. STEC infections usually last five to seven days [1]. Mild E. coli gastroenteritis and some UTIs caused by E. coli can go away on their own. Recovery can take about a week without any treatment [1].
Can you die from E. coli? Yes, E. coli infections can be deadly. A review of studies from high-income countries estimated that about 12% of adults with an E. coli bloodstream infection die [7]. Other estimates of the death rate from E. coli infections are around 17%, with results varying widely between studies (from 8% to 35%) [1]. In general, E. coli UTIs are less likely to be fatal than other kinds of E. coli infections. Sepsis is the most common cause of death in people with E. coli infections [1]. People who are younger than 1 or older than 44, who have a respiratory infection, or who have an infection that doesn't respond to antibiotics have higher mortality rates [1].
When should you see a healthcare provider?
See a healthcare provider if you have diarrhea for more than three days, symptoms of a UTI, or other health concerns [1]. Other guidance sets a shorter limit: contact a healthcare professional if diarrhea lasts more than two days [5].
When should you go to the ER?
Go to the nearest emergency room or seek immediate medical care if you can't keep any fluids down, have bloody diarrhea, are vomiting frequently, have a fever higher than 103 degrees Fahrenheit (39.4 degrees Celsius), are peeing very little, have confusion or other mental changes, or are very weak or lethargic [1].
Questions to ask your doctor
It might be helpful to ask a healthcare provider: What medications are safe for me to take? What strain of E. coli do I have? How can I prevent E. coli from spreading? How can I prevent this in the future?
How can you prevent an E. coli infection?
The most important thing you can do to protect against E. coli infections is to wash your hands. It's particularly important to wash them thoroughly with warm water and soap before and after cooking and after handling raw meat or poultry, and after using the restroom, changing diapers, or contact with animals [1].
You can also reduce your risk of an E. coli infection by following safe food preparation procedures.
Do | Don't |
Wash hands with warm water and soap before/after cooking, after restroom use, diaper changes, and animal contact | Don't drink unpasteurized milk or ciders |
Rinse all raw fruits and vegetables under running water before eating | Don't defrost frozen meat unwrapped on the counter — keep it in a separate plastic bag when thawing |
Cook all meat to a safe temperature before eating | Don't rinse meat before cooking — washing can spread bacteria to surfaces, utensils, and other food |
Use plastic, silicone, or ceramic cutting boards for raw meat (wooden boards are harder to clean completely) | Don't put cooked meat on a plate that held raw meat |
Use different surfaces for different food types; if you don't have separate cutting boards, wash thoroughly with soap and hot water after raw meat | Don't leave leftovers out — refrigerate them right away |
Color alone does not show whether meat is cooked through, so use a meat thermometer: hamburgers should reach at least 160 degrees Fahrenheit (71 degrees Celsius) at the thickest point [5]. Rinsing produce may not remove all E. coli, especially from leafy greens [5].
E. coli is one of the many bacteria that can live in our bodies without harming us. But some strains can make us sick, especially if they get into places they aren't supposed to be. Many E. coli infections can go away on their own. See your provider if your symptoms last more than a few days or are severe.
Key Takeaways
Most E. coli strains in your gut are harmless — a few even help you digest food. Problems start when harmful strains slip in through contaminated food, unpasteurized drinks, unsafe water, or unwashed hands. The good news: most infections are short-lived and resolve with simple hydration. The critical exceptions are STEC infections, which must never be treated with antibiotics or anti-diarrheals, and any infection that brings bloody diarrhea, high fever, or signs of dehydration. Wash your hands, cook your meat, skip raw milk, and call your provider if symptoms linger past three days.
Take the Next Step
Start with the handwashing and food-safety checklist above. If you or your child develops diarrhea lasting more than three days, urinary symptoms, or any of the ER warning signs, talk to a healthcare provider today — a simple stool test can identify the strain and point to the right care.
Related reading: urinary tract infections (UTIs), sepsis, food poisoning, traveler's diarrhea, pneumonia, prostatitis, ulcerative colitis
Frequently Asked Questions
1. What is an E. coli infection?
An E. coli infection is any illness you get from strains of Escherichia coli bacteria. It most often causes gastroenteritis — watery, sometimes bloody diarrhea, stomach cramps, and low fever — when harmful strains are swallowed. E. coli that normally lives in the gut can also cause UTIs if it reaches the urinary tract. About 265,000 STEC infections occur in the U.S. each year.
2. How do you get an E. coli infection?
Most harmful E. coli strains spread through the fecal-oral route — invisible fecal bacteria enter your mouth and digestive tract. You can get it from undercooked meat, raw produce that isn't washed well, unpasteurized milk, cider, or juice, contaminated water (lakes, pools, unsanitized drinking water), and surfaces touched after contact with feces. Not wiping properly can also move E. coli to the urinary tract and cause a UTI.
3. How long does an E. coli infection last?
Depending on the type of infection, symptoms last from two days to two weeks. STEC infections usually last five to seven days. Mild gastroenteritis and some UTIs can go away on their own, with recovery taking about a week without treatment.
4. Is E. coli contagious?
Yes. E. coli spreads from person to person, though not through sneezing or coughing. You can catch it by caring for someone with an infection — especially through contact with their poop — or from objects, surfaces, or food they've touched without washing their hands well enough.
5. Can E. coli go away on its own?
Mild E. coli gastroenteritis and some E. coli UTIs can go away on their own, with recovery in about a week. However, always check with a provider if you have severe or long-lasting diarrhea, abdominal pain, pain when you pee, or are peeing very little.
6. Why can't you take antibiotics for some E. coli infections?
Providers don't treat STEC infections with antibiotics or antidiarrheal medicines because these medications can increase your risk of hemolytic uremic syndrome (HUS), a condition that causes blood clots and kidney damage. Instead, STEC is managed with monitoring and fluids. Other types — like UTIs, meningitis, or sepsis — are treated with antibiotics.
7. What is the most dangerous type of E. coli?
Shiga toxin-producing E. coli (STEC), especially the O157:H7 subtype, is the most likely to cause severe illness. It releases Shiga toxin that damages cells, can cause bloody diarrhea, and leads to HUS in about 5% to 10% of cases. STEC is also the most common cause of E. coli outbreaks and serious illness in the U.S.
8. Can E. coli be deadly?
Yes. A review of studies from high-income countries estimated that about 12% of adults with an E. coli bloodstream infection die; other estimates are around 17%, ranging from 8% to 35%. Sepsis is the most common cause of death. E. coli UTIs are less likely to be fatal than other types. Mortality is higher in people younger than 1 or older than 44, with respiratory infections, or with infections that don't respond to antibiotics.
9. When should I go to the ER for an E. coli infection?
Go to the nearest emergency room if you can't keep fluids down, have bloody diarrhea, are vomiting frequently, have a fever above 103°F (39.4°C), are peeing very little, have confusion or other mental changes, or feel very weak or lethargic. See a provider if diarrhea lasts more than three days or if you have UTI symptoms.
10. How can I prevent an E. coli infection?
Wash your hands thoroughly with warm water and soap — especially before and after cooking, after restroom use, diaper changes, and animal contact. Avoid unpasteurized milk and ciders, rinse raw fruits and vegetables, cook meat to a safe temperature, never rinse raw meat before cooking, use separate cutting boards for raw meat, and refrigerate leftovers right away.
11. Can babies get E. coli infections?
Yes. Babies sometimes get E. coli infections during birth, and newborns and young children are among the groups at greatest risk. The E. coli K1 strain can cause meningitis in newborns, which is why prompt medical evaluation of sick infants is important.
References
Cleveland Clinic. E. coli Infection. Cleveland Clinic. Nov. 22, 2023. https://my.clevelandclinic.org/health/diseases/16638-e-coli-infection
Sevilla P, Martínez A, Nuevo DV, Córdoba JG, Camarena JJ. Impact of antibiotic treatment on hemolytic uremic syndrome risk in Escherichia coli O157 infections: a comprehensive systematic review and meta-analysis. Eur J Clin Microbiol Infect Dis. 2025;44(8):1763-1778. doi:10.1007/s10096-025-05145-1. PMID: 40304896.
Freedman SB, Xie J, Neufeld MS, et al. Shiga toxin-producing Escherichia coli infection, antibiotics, and risk of developing hemolytic uremic syndrome: a meta-analysis. Clin Infect Dis. 2016;62(10):1251-1258. doi:10.1093/cid/ciw099. PMID: 26917812.
Imdad A, Nelson JR, Tanner-Smith EE, Huang D, Gomez-Duarte OG. Interventions for preventing diarrhoea-associated haemolytic uraemic syndrome. Cochrane Database Syst Rev. 2025;4(4):CD012997. doi:10.1002/14651858.CD012997.pub3. PMID: 40277027.
Mayo Clinic Staff. E. coli - Symptoms and causes. Mayo Clinic. June 2, 2026. https://www.mayoclinic.org/diseases-conditions/e-coli/symptoms-causes/syc-20372058
Mayo Clinic Staff. E. coli - Diagnosis and treatment. Mayo Clinic. June 2, 2026. https://www.mayoclinic.org/diseases-conditions/e-coli/diagnosis-treatment/drc-20372064
Bonten M, Johnson JR, van den Biggelaar AHJ, et al. Epidemiology of Escherichia coli Bacteremia: A Systematic Literature Review. Clin Infect Dis. 2021;72(7):1211-1219. doi:10.1093/cid/ciaa210. PMID: 32406495.
Medical Disclaimer
This article is for informational purposes only and does not constitute medical advice. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read here.
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