E. coli
E. coli are common bacteria that usually live harmlessly in intestines, but some strains can cause diarrhea, urinary infections, outbreaks, and serious kidney complications.
What E. coli is
E. coli, short for Escherichia coli, is a large group of bacteria. Many strains are normal residents of the gut and help mark fecal contamination when found in food or water. The problem is that some strains carry traits that let them cause intestinal disease, urinary tract infections, bloodstream infections, meningitis, or other illness.
Pathogenic strains
Health agencies often group disease-causing E. coli by how they behave. Shiga toxin-producing E. coli, or STEC, is a major foodborne concern because it can damage the gut and sometimes the kidneys. Other groups can cause traveler diarrhea, persistent diarrhea, invasive intestinal disease, or infections outside the gut.
How people are exposed
People can swallow harmful E. coli through contaminated food, water, animal contact, or hands and surfaces. Undercooked ground beef, raw milk, unpasteurized juice, contaminated produce, recreational water, petting zoos, farms, and close contact with a sick person can all be part of transmission chains.
Symptoms
Intestinal E. coli infection can cause stomach cramps, diarrhea, vomiting, and fever. STEC illness often begins with severe cramps and diarrhea that may become bloody. Some people have mild illness, while others become dehydrated or develop complications several days after diarrhea starts.
Hemolytic uremic syndrome
Hemolytic uremic syndrome, or HUS, is a serious complication linked to some STEC infections. It can damage red blood cells, lower platelet counts, and injure the kidneys. Children and older adults are at higher risk, and warning signs such as decreased urination, unusual fatigue, paleness, or bruising need urgent medical attention.
Diagnosis and treatment
Clinicians may test stool for E. coli O157 and non-O157 STEC, including tests for Shiga toxin or toxin genes. Treatment usually focuses on fluids and careful monitoring. Antibiotics and anti-diarrheal medicines are not automatically appropriate for suspected STEC infection because some treatments may increase complication risk.
Prevention
Prevention uses the same practical habits that protect against many foodborne infections: cook ground beef thoroughly, avoid raw milk and unpasteurized juice, wash hands after animal contact and bathroom use, rinse produce, prevent cross-contamination in the kitchen, and avoid swallowing water from lakes, pools, or splash areas.
Outbreak investigations
E. coli outbreaks can be tied to foods, restaurants, farms, animal venues, water, or person-to-person spread. Public-health investigators compare interviews, purchase records, environmental clues, and laboratory results. Genetic sequencing can show whether bacteria from different people are closely related, helping narrow the source.
Why it matters
E. coli matters because the same name covers both ordinary gut bacteria and strains capable of causing severe outbreaks. Understanding that distinction helps people take food safety seriously without treating every mention of E. coli as equally dangerous.