How Do You Get E. Coli?

Most types of E. coli bacteria live peacefully in and around us all the time—in our guts, in the intestines of other animals, and in land and water. Some are even “good” bacteria, lending a hand in the digestion process. But then there are the less peaceful varieties, the types of E. coli that can cause bloody diarrhea, nausea, vomiting, cramps, and more—otherwise known as food poisoning.

These “bad” bacteria are usually found in human or animal feces. About 85% are transmitted to humans through food, often ground beef that becomes contaminated during processing, Robert Glatter, MD, an emergency physician with Lenox Hill Hospital in New York City, tells Health.

The ground beef that ends up in supermarkets and eventually on dinner tables usually combines meat from many different animals, increasing the risk that it's contaminated.

RELATED: Everything You Need to Know About E. Coli Symptoms—in Case There’s Another Outbreak

The network of contamination can expand from there: Raw vegetables that have come into contact with runoff from cattle farms are another cause of E. coli infections. Spinach, lettuce, and alfalfa sprouts are common culprits.

Cattle themselves can transmit E. coli bacteria another way—through their milk. “Bacteria can be spread from the udders of a cow to infect the milk,” says Dr. Glatter. From there, E. coli can go on to infect soft cheeses.

That’s why it’s so important to drink only pasteurized milk. The same goes for juices made from fruits and vegetables: If they haven’t been pasteurized, they may still harbor E. coli passed on by the original fruits or vegetables.

It gets stranger. We’re sad to tell you that even raw cookie dough can harbor E. coli—not from the eggs in the batter (which could have salmonella anyway) but from the flour. Flour comes from grains that grows in field where cattle and other animals may have traipsed.

Water is another potential reservoir of E. coli. “Feces from humans or animals that are infected with E. coli can potentially get into pools as well as the water supply,” says Dr. Glatter. “People can also become infected with E. coli when a contaminated water supply has not been adequately treated with chlorine or when people accidentally swallow contaminated water while swimming in a lake or pool infected with feces.”

It doesn’t take much to make you sick from any of these sources, just a taste of food or a mouthful of water.

RELATED: 14 Foods That Can Make You Sick

Is E. coli contagious?

You can get E. coli from either human-to-human or animal-to-human contact. Some people have been known to pick up E. coli at county fairs, petting zoos, and farms. Or you may pick it up from another person.

“This typically occurs when an infected person does not wash his or her hands well after a bowel movement,” explains Dr. Glatter. “E. coli can spread from an infected person's hands to other people or even to objects.”

RELATED: Is It Food Poisoning—or Stomach Flu? Here’s How to Tell

Preventing E. coli

The good news is that even though dangerous strains of E. coli bacteria may be all around us, you don’t have to get sick from them. Start by making sure ground beef is cooked to 160 degrees Fahrenheit at its thickest point.

“If the infected meat is not cooked to a high enough temperature, E. coli bacteria can survive and lead to infection if you consume the meat,” says Dr. Glatter.

Don’t rely on the color of the meat to reassure you. Use an actual meat thermometer when you're cooking at home. (Steaks and roasts should be cooked to at least 145 degrees, according to the CDC.) If you’re at a restaurant, it’s safest to order hamburgers medium or well-done.

Only drink pasteurized milk and juice, and wash all produce well.

When you’re preparing food at home, go for plastic or ceramic cutting boards, which are easier to clean than wooden ones. And make sure you don’t cross-contaminate by washing any utensils or countertops that have come into contact with raw meat. Don’t let raw meat touch any other foods, and don’t defrost it on the counter. (Do it in the refrigerator instead.)

And then, of course, there’s washing your hands—after handling food, after eating, after going to the bathroom, after handling diapers, after touching animals, before feeding your children, and just about any other time you happen to think about it. Soap and water is always best, but an alcohol-based sanitizer (at least 60% alcohol) will often do in a pinch.

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