About E. coli

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Symptoms of E. coli infection

What are the signs and symptoms of infection after Shiga toxin-producing E. coli are ingested?

The colitis caused by Escherichia coli (E. coli) O157:H7 is characterized by severe abdominal cramps, diarrhea that typically turns bloody within 24 hours, and sometimes fever. [4] 


The incubation period—that is, the time from exposure to the onset of symptoms—in outbreaks is usually reported as 3 to 4 days, but may be as short as 1 day or as long as 10 days. [4, 13, 26]  Infection can occur in people of all ages but is most common in children. [26] 

Unlike other E. coli pathogens, which remain on intestinal surfaces, Shiga toxin-producing bacteria, like O157:H7, are invasive. [1] After ingestion, E. coli bacteria rapidly multiply in the large intestine and then bind tightly to cells in the intestinal lining.  [1, 26] This snug attachment facilitates absorption of the toxins into the small capillaries within the bowel wall.  [1, 33, 45] Once in the systemic circulation, Shiga toxin becomes attached to weak receptors on white blood cells, thus allowing the toxin to “ride piggyback” to the kidneys where it is transferred to numerous avid (strong) Gb3 receptors that grasp and hold on to the toxin. [33]

Inflammation caused by the toxins is believed to be the cause of hemorrhagic colitis, the first symptom of E. coli infection, which is characterized by the sudden onset of abdominal pain and severe cramps. [29, 42] Such symptoms are typically followed within 24 hours by diarrhea, sometimes fever. [1, 4]

As the infection progresses, diarrhea becomes watery and then may become grossly bloody; that is, bloody to the naked eye.  E. coli symptoms also may include vomiting and fever, although fever is an uncommon symptom.

On rare occasions, E. coli infection can cause bowel necrosis (tissue death) and perforation without progressing to hemolytic uremic syndrome (HUS)—a complication of E. coli infection that is now recognized as the most common cause of acute kidney failure in infants and young children.  In about 10 percent of E. coli cases, the Shiga toxin attachment to Gb3 receptors results in HUS. 

The duration of an uncomplicated illness can range from one to twelve days. [4, 23]  In reported outbreaks, the rate of death is 0-2%, with rates running as high as 16-35% in outbreaks involving the elderly, like those that have occurred at nursing homes. [23]

Shiga toxin–producing E. coli (STEC) cause approximately 100,000 illnesses, 3,000 hospitalizations, and 90 deaths annually in the United States.  [39, 54] As noted, most reported STEC infections in the United States are caused by E. coli O157:H7, with an estimated 73,000 cases occurring each year. [39] According to the CDC:

Non-O157 STEC bacteria also are important causes of diarrheal illness in the United States; at least 150 STEC serotypes have been associated with outbreaks and sporadic illness. In the United States, six non-O157 serogroups (O26, O45, O103, O111, O121, and O145) account for the majority of reported non-O157 STEC infections. [54]

Persons with non-O157 STEC tend to have less severe illness, but some non-O157 STEC members can cause very severe infections, including those that result in HUS and death.  Non-O157 STEC that cause HUS overwhelmingly produce Shiga toxin 2 with or without Shiga toxin 1.  As with E. coli O157:H7, more severe disease results from Shiga toxin 2 production by non-O157 STEC.

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