Escherichia coli (E. coli) diarrhea, frequent, liquid bowel movements caused by E. coli bacteria, which normally inhabit the digestive tract of humans without harm. However, a strain of E. coli (enterohemorrhagic) that is most commonly associated with contaminated hamburger meat causes bloody diarrhea and sometimes death. Another type of E. coli bacteria is responsible for many cases of traveler’s diarrhea.