E. coli, just enough information

According to the CDC, the latest outbreak is due to E. coli O157—a strain of the E. coli bacterium that’s caused at least one food-borne outbreak in the U.S. each year since 2006.

These bacteria are so harmful to humans (and successful) because they make a Shiga toxin that undermines our immune system while helping it to get passed on to another host. They don’t make animals sick, which make cattle, for example, conduits for the disease to reach humans.

Shiga toxin-producing E. coli (STEC)

Let’s say you eat romaine contaminated with the bacterium. Inside your body, as the bacteria reproduce, they produce a Shiga toxin as part of their strategy for finding a new host. The toxins cause symptoms like a low-grade fever, stomach cramps, diarrhea (often bloody) and vomiting. People get the bacteria by ingesting it and it’s spread through fecal material.

how it’s spread

food and water

  • E. coli exist in cows (and don’t make them sick). When it’s on a cow’s udder or on milking equipment it can get into raw milk. Pasteurizing the milk kills the bacteria.
  • E. coli is found in cows, but chickens, deer, sheep, and pigs have also been known to carry it (they don’t get sick from it, though). Meat can be contaminated during slaughter. Ground meat is considered more risky because E. coli can be mixed through the meat in the grinding process.
  • Fresh produce can be contaminated with E. coli when it comes in contact with the runoff from cattle farms (that contains feces from infected cattle). The bacteria can also be transferred to fresh produce during harvesting and packing, if the workers or the equipment carry the bacteria.


  • E. coli can easily travel from person to person if someone has the bacteria on their hands, most often when infected adults and children don’t wash their hands properly.
  • Children who visit petting zoos and animal barns can also contract the infection after touching the animals.

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