What Causes E. Coli Infections?

Escherichia coli, more commonly known as just E. coli, is a harmless bacteria naturally found in your intestines. But some types, including Shiga toxin-producing E. coli (STEC) and enterotoxigenic E. coli (ETEC), release toxins in your body and cause infections to develop. The most common cause of these infections is consuming contaminated food or water. But, you might also develop symptoms if you don't wash your hands properly or are in frequent contact with farm animals.

E. coli infections mostly affect your gastrointestinal (GI) tract—the passageway in your digestive system that connects your mouth to your anus. As a result of the infection, you'll likely experience symptoms such as diarrhea, abdominal pain, and nausea or vomiting. Knowing the causes and how to reduce your risk of the infection can prevent these symptoms from developing.

Common Causes

E. coli bacteria spread through the oral-fecal route. This means that you can catch the bacteria when infected feces (poop) comes into contact with your food or drinking water. The following are the most common ways that your food can get contaminated:

• Eating food that was prepared by a person who didn't wash their hands after using the bathroom or changing diapers
• Swallowing contaminated water accidentally when swimming
• Consuming undercooked meat (especially beef) or unwashed vegetables
• Making food on unclean cooking surfaces
• Coming into contact with contaminated environments like hospitals, daycare centers, and nursing homes
• Having direct skin-to-skin contact or hand-to-mouth contact with someone who has been exposed to E. coli bacteria
• Drinking unpasteurized (or, raw) milk or juices
• Taking care of farm animals (like cattle, goats, or sheep) and then eating with unclean hands
  
• Petting zoo animals and not washing your hands before making contact with your mouth

Is E. Coli Hereditary? 

No matter your genetics, anyone can get an E. coli infection. But, many people who are exposed to the infection can carry the bacteria without having any signs of E. coli. However, research does show some early evidence that your genes can influence how vulnerable you are to contracting the infection and developing symptoms.

Certain genes are associated with your body’s immune response and can influence your chance of having symptoms of the infection. For E. coli infections specifically, researchers have linked these genetic changes to mutations in the interleukin 8 (IL-8) genes and histocompatibility complex (HLA) genes. But, research on how genetics increase your risk of E. coli infections is ongoing. An early study found that changes in as many as 29 genes in your DNA can raise your risk of infections.

More research is needed to fully understand how inheritable your immune system is to develop an E. coli infection. Some studies have noted that environmental factors have more influence than genes in healthy people. Still, a family history of weakened immunity or being born with an autoimmune disorder can increase your chances of having an infection and experiencing symptoms.

Who Gets E. Coli Infections? 

While E. coli infections can affect anyone, certain populations are more like to develop infections and have more severe episodes or complications. The following factors may increase your risk of infections and complications:

• Age: E. coli infections are most common in infants and children younger than the age of five and among adults over the age of 60 years old. These demographics are also more likely to experience severe symptoms and complications, due to lowered immunity.
• Socioeconomic status: Living in an area with poor sanitation and limited resources to clean water and food increases your risk of developing the infection. Traveling to these regions may also cause an E. coli infection or traveler’s diarrhea.
• Geographic location: Since cattle and livestock can carry the E. coli bacteria, living or working in a rural or agricultural area increases the odds of having the infection.

Risk Factors 

Your risk of developing an E. coli infection and experiencing symptoms rises if you have increased exposure to the bacteria or a weakened immune system. Aside from the primary causes of the infection—such as eating undercooked food or poor handwashing habits—the most common factors that can increase your risk of the infection include:

• Working in a clinical or hospital environment with easy access to germs
• Having health conditions that affect immunity, such as diabetes, HIV/AIDS, or cancer
• Undergoing chemotherapy or taking medications that weaken your immune system

A Quick Review 

E. coli infections commonly cause symptoms that affect your GI tract, including diarrhea, nausea, and abdominal pain. The most common cause of the infection is through the oral-fecal route—meaning that infected feces (poop) come into contact with your hands and mouth.

You may be at risk of the infection if you eat food or drink water that's contaminated, don't wash your hands properly after using the restroom or changing a diaper, or come into contact with farm or zoo animals. The risk of infection is also higher if you're under the age of 5, older than 60 years old, have an autoimmune disorder, or live in rural or poor sanitation areas.

If you suspect you have an E. coli infection or may be at risk of contracting these bacteria, contact your healthcare provider for proper testing. In most cases, E. coli infections go away on their own. But, if you have a weakened immune system, treatment can help reduce symptoms and prevent complications.