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Escherichia coli (E. coli) Infection, including Haemolytic Uraemic Syndrome (HUS)

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Reporting Obligations

Confirmed and suspected cases of VTEC and HUS shall be reported to the local Health Unit.

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Epidemiology

Aetiologic Agent

Verotoxin-producing Escherichia coli (VTEC), also known as Shiga toxin-producing E. coli (STEC), is a highly pathogenic subtype of E. coli. VTEC are distinguished from other E. coli by the ability to produce Shiga toxins (also referred to as verotoxins), or by the presence of genes encoding those toxins. E. coli O157:H7 is most commonly associated with infection in humans. However, the clinical relevance of non-O157 subtypes of VTEC have been increasingly recognized.

Clinical Presentation

Self-limiting enteric disease in infants and adults; characterized by bloody or non-bloody diarrhea and severe abdominal pain or cramping. Fever is not present in most cases and symptoms usually last fewer than five days.

Most individuals recover without residual sequelae, however, complications such as hemorrhagic colitis and hemolytic uremic syndrome (HUS) can occur. HUS occurs in about 15% of infected children as well as in a small number of adults, particularly the elderly.

Modes of Transmission

Transmitted by the fecal-oral route mainly by ingestion of contaminated food and direct contact with animals and their environment. Ground beef is a common source of infection, but other known sources include fresh produce (such as lettuce, spinach, coleslaw, sprouts and melons) and unpasteurized milk and beverages (such as apple cider and orange juice).

Waterborne transmission can occur through the ingestion of contaminated drinking water or recreational water.

Animal to person transmission can occur at farms and petting zoos.

Person-to-person transmission most frequently occurs in settings (e.g., day nurseries) where personal hygiene practices are inadequate.

Incubation Period

2–10 days with a median of 3–4 days. HUS typically develops 7 days (up to 3 weeks) after onset of diarrhea.

Period of Communicability

Variable, as long as organisms are excreted; the duration of excretion of the pathogen is typically 1 week or less in adults but can be 3 weeks in one third of children. Prolonged carriage is uncommon.

Risk Factors/Susceptibility

The infectious dose is very low. Little is known about differences in susceptibility and immunity, but infections occur in persons of all ages. Children under five years are most frequently diagnosed with infection and are at greatest risk of developing HUS. The elderly also appear to be at increased risk of complications.

  • Close contact with case
  • Animal contact
  • Poor hand hygiene practices
  • Consumption of raw/undercooked meat/poultry
  • Consumption of unpasteurized milk/milk products
  • Consumption of contaminated water
  • Travel outside province/country within last 10 days

Diagnosis and Laboratory Testing

Routine screening for non-O157 VTEC is not routinely performed in most laboratories. This testing can be performed at the Public Health Ontario Laboratories if specifically requested.

Enteric culture specimens are accepted only from health units at the Public Health Lab. If you are a clinician, please use a community laboratory to perform your testing. Confirmation and speciation performed at Public Health Lab.

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Treatment and Case Management

Use of antibiotics is not recommended. Treatment of VTEC is largely supportive and may require hospital admission.

Provide information to patients on personal prevention measures (careful hand hygiene after defecation, sexual contact and before preparing or eating food). Household members should be assessed for symptoms. Instruct patients to keep samples of implicated foods for testing by public health.

Exclude symptomatic food handlers, healthcare providers, and day care staff and attendees until the provision of 2 consecutive negative stool specimens or rectal swabs taken at least 24 hours apart and at least 48 hours after the completion of antibiotic and/or anti-diarrheal therapy medications, if these medications have been used.

Patient Information

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Additional Resources

Public Health Agency of Canada. “E. coli.”

References

Heymann, D.L. Control of Communicable Disease Manual (19th Ed.). Washington, American Public Health Association, 2008.

Ministry of Health and Long-Term Care, Infectious Diseases Protocol, 2019.