Causes of E. coli (Escherichia coli) infection

Learn about illness due to E. coli, how E. coli is spread and where it is found.

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What causes an E. coli infection?

E. coli infection is caused by E. coli bacteria.

How is E. coli spread?

E. coli bacteria can be spread through contact with:

  • infected people
  • infected animals
  • contaminated surfaces, foods or liquids

You can be exposed to E. coli by:

  • eating:
    • raw or undercooked beef, especially ground beef
    • unpasteurized milk products, such as raw milk cheese
    • contaminated raw fruits and vegetables, such as leafy greens or sprouts
  • drinking:
    • untreated water
    • unpasteurized juices
    • unpasteurized (raw) milk
    • mishandling or undercooking food contaminated with E. coli
    • coming into contact with the feces of infected animals or people

Both animals and people can be carriers of E. coli. This means they can be infected with the bacteria and can spread it to others without showing signs of illness.

Adults who have an E. coli infection can infect others for up to a week. However, in some cases, children can infect others for up to 3 weeks.

Where is E. coli found?

E. coli are bacteria that live naturally in the intestines of some animals, and can be found in their feces. These animals include:

  • cattle
  • goats
  • sheep

How do food and water become contaminated?

Water can become contaminated with the bacteria when feces from infected people or animals, including carriers, enter the water supply.

Food can become contaminated with E. coli in many ways. Some of the most common ways include:

  • during the processing of raw meat
  • when food is handled by a person infected with E. coli
  • during the growing or harvesting of fruits and vegetables
    • this is possible if the produce comes into contact with contaminated manure or water
  • when raw food is handled improperly, which can lead to cross-contamination

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