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E. Coli Fast facts

by Julia Singer

What is E. coli and why do we test for it?  

Escherichia coli (E. coli) are a category of rod-shaped bacteria that exist naturally in the intestines of nearly 90% of humans[1]. E. coli are some of the most common types of bacteria found in our intestines. Within the human gut, naturally occurring E. coli is not only harmless, but also beneficial in facilitating digestion[2]. Naturally occurring E. coli strains found in our bodies are good for human health. 

The problem is that there are hundreds of E. coli strains. Harmful E. coli strains (those that do not occur naturally in our gut) cause a host of illnesses, ranging from diarrhea or nausea to kidney disease or septic shock[1]

Because E. coli is found in the intestines of most living things, scientists measure the presence of E. coli in water. High concentrations of E.coli point to contamination of a water system via wastewater system overflow, excessive animal waste runoff or other harmful bacteria, including viruses. People should avoid waterways with high E. coli concentrations, as there is a high likelihood of getting sick from harmful E. coli. 

Common foods contaminated with harmful E. coli:

Raw fruits and vegetables (e.g., sprouts, spinach, and leafy greens)[3,4] Raw or undercooked meats (e.g., ground beef and chicken)[3,4]

How does E. coli make you sick?

There are a few potential ways of developing a harmful E. coli infection. We come in contact with harmful E. coli via person to person, food-borne, and fecal to oral transmission. This is why it is always good to cover your cough, clean and cook your food properly, and wash your hands[6]! People who are carrying harmful E. coli may pass the infection onto other people. Farm animals can serve as excellent hosts for harmful E. coli., as they are found often in the gut of cattle[7]. By not washing our hands or our phones, we may unknowingly come in contact with harmful E. coli from feces. Infected feces also can enter into waterways via farm runoff, storm overflows, and wastewater spills. 

Preventing Infection

To prevent E. coli infection at home, eating out, or on the job, it is crucial to practice proper hygiene. 

  • Wash hands thoroughly for 20 seconds with warm soap and water after using the bathroom and before cooking and eating[7]
  • When preparing meals, keep raw fruits and vegetables separated from raw meats. Meats should also be cooked to optimal internal temperature. 
    • According to the CDC, raw beef steaks and roasts should reach an internal temperature of 145ºF. Pork and ground beef should be cooked to an internal temperature of 160ºF, and lastly, chicken must be cooked until it reaches 165ºF8. Meat thermometers are a handy kitchen tool to ensure the proper temperature is reached – be sure to clean the thermometer thoroughly to avoid cross-contamination. 
  • Maintain cleanliness in fridges, freezers, cabinets, and pantries to prevent possible contamination. A cleaning mix of one tbsp bleach and one gallon hot water is a suitable alternative sanitizer[9]

Frequently Asked Questions

1. What do E. coli infection symptoms look like? 

Symptoms include abdominal cramps, diarrhea, vomiting, and a mild to moderate fever. Symptoms can last upwards of 7 days and illness can range from very mild to incredibly severe, to sometimes, fatal. Symptoms usually start off mildly and get worse each day over several days. If you experience blood in your stool or urine, see a medical professional immediately [10]

2. How long does it take for symptoms of E. coli infection to manifest? 

This period of developing symptoms following exposure varies from person to person. The average period of time is three to four days; but symptoms can appear in as short as one day and as long as 10 days[10,11]

3. Are certain individuals more vulnerable to infection than others? 

Yes, children under the age of 5 and adults aged 65 and over are at risk of developing a severe illness due to E. coli infection. They are also more likely to develop kidney problems or damage. Additionally, individuals with compromised immune systems should be cautious when handling raw meats and produce, as they are more susceptible to infection[10]

4. What is the best treatment for E. coli infections? 

First, it is imperative to visit your doctor if you suspect you have an E. coli infection, especially if you have persistent diarrhea or blood in your stool[12]. They will likely use a stool sample test to determine if you have an infection. The best treatment for infection from E. coli is sufficient hydration. Antibiotics and antidiarrheal medications are not recommended for E. coli infections because sometimes they worsen symptoms[12]. A medical professional can determine what, if any, medication is appropriate for you.


1    Mueller M, Tainter CR. Escherichia coli Infection. [Updated 2023 Jul 13]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from:

2    FAQ: E. Coli: Good, Bad, & Deadly: “What is true for E. coli is true for the elephant”. Washington (DC): American Society for Microbiology; 2011. Available from: 10.1128/AAMCol.1-2011

3    Nutrition C for FS and A. Escherichia coli (E. coli). U.S. Food And Drug Administration. Published March 28, 2019.

4    World Health Organization: WHO. E. coli. Published February 7, 2018.,and%20faecal%20contamination%20of%20vegetables.

5    Menge C. Molecular Biology of Escherichia Coli. Shiga Toxins’ Effects on Mammalian Cells. Toxins (Basel). 2020;12(5):345. Published 2020 May 23. doi:10.3390/toxins12050345

6    E. coli (Escherichia coli): Questions and Answers. Centers for Disease Control and Prevention.

7   Ray R, Singh P. Prevalence and Implications of Shiga Toxin-Producing E. coli in Farm and Wild Ruminants. Pathogens. 2022; 11(11):1332.

8    E. coli (Escherichia coli): Prevention. Centers for Disease Control and Prevention.

9    World Health Organization: WHO. E. coli. Published February 7, 2018.,and%20faecal%20contamination%20of%20vegetables.

10  E. coli (Escherichia coli): Questions and Answers. Centers for Disease Control and Prevention.

11   Nutrition C for FS and A. Escherichia coli (E. coli). U.S. Food And Drug Administration. Published March 28, 2019.

12   What is E. Coli? WebMD. Published February 6, 2017.

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