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Escherichia coli, o�� E. coli, is a type of bacteria commonly found in human and animal intestines. Most E. coli strains are harmless, says Dr. Heidi Torres, Assistant Professor of Clinical Medicine in the Division of Infectious Diseases and Assistant Hospital Epidemiologist at �ձ�avɫ��Ƭ, and they’re even a beneficial part of the gut’s microbial ecosystem. However, certain strains can cause illness, with symptoms including diarrhea, urinary tract infections and pneumonia.  ��

To get a handle on the recent E. coli outbreaks in the U.S., see Dr. Torres’s answers to your FAQs below.��

Which E. coli strains are responsible for the two E. coli outbreaks this fall?��

E. coli O157:H7, also known as enterohemorrhagic E. coli, can lead to intestinal infections accompanied by bloody diarrhea, among other severe symptoms. In a recent outbreak identified this �����ٴDz����, E. coli O157:H7 was traced to sliced onions served at various McDonald's locations, resulting in 104 known cases across 14 states, including New York.��

Another strain, E. coli O121, can cause similar symptoms. That strain was responsible for a separate outbreak identified in mid-November, linked to bagged organic carrots, with 39 known cases across 18 states reported thus far.����

However, according to the Centers for Disease Control and Prevention (CDC), the actual number those made sick by the two E. coli strains is probably significantly higher. That’s because some people improve on their own and aren’t included in the data.��

How can people become infected with a harmful type of E. coli?��

“People typically become infected with harmful strains of E. coli through contaminated food and water,” Dr. Torres says. “During processing, meat may be contaminated with E. coli from cattle intestines; the bacteria can survive if your food isn’t cooked thoroughly.����

“Unpasteurized milk can also carry E. coli if it’s contaminated from the cattle,” she adds. “As well, water sources exposed to human or animal waste can transmit bacteria to vegetables and other foods or directly infect individuals who come into contact with contaminated water. Close contact with an infected person can further spread E. coli b�����ٱ������.”��

Who is especially vulnerable to infection?��

As with many infections, young children, older adults and people with weakened immune systems are at greater risk of contracting E. coli and experiencing severe illness.����

“Additionally, taking antacids puts you at increased risk, as stomach acid plays a role in killing swallowed bacteria,” she says.��

What are the most common symptoms of an E. coli infection?��

Symptoms usually begin within a few days and often include stomach cramps, diarrhea (possibly bloody), fatigue, nausea and vomiting. Rarely, she says, “an E. coli infection can lead to hemolytic uremic syndrome (HUS), a serious complication that may cause kidney failure and can be life-threatening.”��

How do you typically treat patients with an E. coli infection?��

Treatment for an E. coli infection involves supportive care, including fluids, electrolytes and rest. These are usually enough to ensure recovery.����

“Antibiotics and antidiarrheals are not routinely recommended and should be avoided for certain E. coli strains”--including the two current ‘troublemakers,’ O157:H7 and O121. Paradoxically, these medications may increase the risk of HUS.��

For other E. coli strains with a lower risk of HUS, antibiotics may be administered to those with severe or prolonged diаrrhеа or those at risk for severe disease. The distinction between strains can often be made through stool testing.��

When is it time for a patient to call their doctor?��

If you suspect that you have been exposed to E. coli, or if you’re experiencing any of the symptoms described above, make an appointment with an infectious disease specialist.��