The recent report of a multi-state outbreak of E. coli 0157:H7 secondary to romaine lettuce may to to parental fears – specifically hemolytic uremic syndrome (HUS). Fortunately the risk of transmission is low. But, just in case you have someone who is worried and seeking reassurance – or actually needs a work up I wanted to provide some information.

What is the extent of the outbreak?

Fortunately there have only been 32 cases of Escherichia coli O157:H7 confirmed across the US per the CDC. Available epidemiologic data has linked it to Romaine lettuce. The CDC has recommended that persons not consume any romaine lettuce, and to clean any areas of their fridge that had recently stored it. It has also been removed form store shelves. The cases were reported between 10-8 and 31. Per the CDC “forty-one percent of ill people have been hospitalized, including one person who developed hemolytic uremic syndrome. No deaths have been reported.”

What should I do if a patient presents because they had a possible exposure?

If the patient is well appearing, and asymptomatic romaine calm, and lettuce be. There are several disease manifestations of E. coli O157:H7, though other shiga toxin producing strains can be implicated as well (STEC). The most worrisome one is obviously HUS.

STEC illness generally starts with nonbloody diarrhea. Stools become bloody by the 2nd or 3rd day – signaling hemorrhagic colitis. Children can have severe abdominal pain and fever in up to ⅓ of cases. It can manifest in symptoms that are similar to intussusception, appendicitis or inflammatory bowel disease. Importantly per the CDC/Red Book “the incubation period for most E coli strains is 10 hours to 6 days; for E coli O157:H7, the incubation period usually is 3 to 4 days (range, 1–8 days).”

E. coli 0157:H7 is identified in stool immunoassays. So, if you see a child with bloody diarrhea now, or during a subsequent outbreak chances are your lab will be performing assays for STEC strains. If you’re not sure – it doesn’t hurt to call and ask.

If the kid has bloody diarrhea and I suspect E. coli O157:H7 what is the treatment?

The overall key is adequate hydration – this can generally be accomplished with electrolyte solutions. Though children who are moderately ill will require IV fluids. Experts state that aggressive fluid resuscitation is most needed over the first 4 days. Do not give anti motility agents (Imodium). Antibiotics remain controversial because of increased association with HUS and are generally not recommended. Patients with hemorrhagic colitis should also have a CBC and renal panel sent to evaluate for anemia, thrombocytopenia and uremia. Blood cultures should be obtained for small infants (<2-3 months of age), septic kids (duh), immunocompromised patients of those with pre-existing conditions putting them at risk for HUS. If these labs are normal 3 days after the diarrhea has ended then risk of developing HUS is low.

What about Hemolytic Uremic Syndrome?

HUS is the most serious sequela of STEC/E. coli O157 infection. It is defined by the following triad:

  1. Microangiopathic hemolytic anemia
  2. Thrombocytopenia
  3. Acute renal dysfunction

Up to 6% of all humans and 15% of children <5 years with laboratory confirmed E. coli O157:H7 develop HUS. The risk is higher in kids 1-4 years old versus infants. HUS develops 7 days to 2 weeks after the onset of diarrhea. Over 50% of HUS patients need dialysis and the case mortality rate is as high as 5%. Neurologic complications can also be seen and include seizures, coma and/or cerebral vessel thrombosis. Worse out comes are seen in leukocytosis (WBC >20,000) , oliguria/anuria, and interestingly almost normal hematocrit. If creatinine clearance and urine protein are normal, along with BP at one year then prognosis is good. Obviously Nephrology involvement is mandated.

Again, antibiotics may be associated with an increased risk of developing HUS. This should be the linchpin of your discussion with parents of children with bloody diarrhea. In general it is best to wait until stool testing is complete. Shigella and campylobacter can benefit from antibiotics, whereas salmonella and STEC don’t.

Take Home Points

  • If you see a child with bloody diarrhea get stool studies and make sure there are specific assays for STEC/O157:H7
  • Adequate hydration oral or IV is the mainstay of therapy
  • Don’t give antibiotics until you know what is in the stool
  • Workup in the ill child with bloody diarrhea includes the aforementioned stool studies plus at least a CBC and Renal. Make sure you get a BP and consider urine studies as well.


Centers for Disease Control and Prevention. Recommendations for diagnosis of Shiga toxin-producing Escherichia coli infections by clinical laboratories. MMWR Recomm Rep. 2009;58(RR-12):1–14.

Escherichia coli Diarrhea. Red Book, 2018. accessed 11/22/18.

Infectious Diarrhea. Pediatric EM Morsels.