Shiga toxin-producing E. coli (STEC)

• Reporting criteria
• The disease and its epidemiology
• Case definition

• Laboratory testing
• Case investigation
• Disease control measures

• References
• Contact

What and how to report to the Colorado Department of Public Health and Environment (CDPHE) or local public health agency  

• All specimens with a positive test for STEC and/or presence of shiga toxin (both O157 and non-O157 serotypes, regardless of specimen source) by culture, enzyme immunoassays (EIA), polymerase chain reaction (PCR), or other form of testing should be reported to public health within four (4) days of the positive test result.
  • All positive STEC laboratory tests should be reported to public health, regardless of symptoms. Public health will make the determination of whether the case meets the case definition.
• Cases should be reported using EpiTrax Reportal, fax, or telephone to CDPHE or local health departments (telephone and fax numbers are listed at the end of this document).
• All potential foodborne, waterborne, and enteric disease outbreaks should be reported immediately to CDPHE or local health departments and entered into EpiTrax, even if the causative agent is not yet known.
  • In general, an “outbreak” is defined as an increase in the number of illnesses above what is normally expected among a specific population, within a given area, over a certain period of time.
  • Specifically, a foodborne disease outbreak occurs when two or more people get the same illness from the same contaminated food or drink.
• If a STEC case is subsequently diagnosed with hemolytic uremic syndrome (HUS), the HUS should be reported as a separate case to public health.

Purpose of surveillance and reporting

• To identify cases for investigation and potential outbreaks
• To monitor trends in disease incidence

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Etiologic agent

There are more than a hundred different serotypes belonging to the group of gram-negative bacteria Escherichia coli, the majority of which cause no human illness. E. coli O157:H7 and several other serotypes (e.g., O26, O111) produce potent cytotoxins, called Shiga toxins. All E. coli that produce Shiga toxin are categorized as Shiga toxin-producing E. coli, or STEC. Only shiga toxin-producing E. colis are reportable conditions in Colorado. 

The STEC serogroup most commonly identified and associated with severe illness and hospitalization in the United States is E. coli O157. However, there are over 50 other serogroups that can also cause illness. Of note, STEC is sometimes referred to as enterohemorrhagic E. coli (EHEC) or verocytotoxin-producing E. coli (VTEC).

Clinical description

The most common symptoms of STEC are diarrhea (often bloody), nausea, vomiting, and abdominal cramps (often severe). Fever is usually absent. Most people recover within 5 to 7 days. Asymptomatic infections may occur. The organism may rarely cause extraintestinal infections.

STEC infection in young children may lead to potentially life-threatening complications, such as HUS in 5-15% of cases. While HUS appears to be less common among people with non-O157 STEC infections, it still occurs.  

For clinical information about HUS, visit the HUS chapter in the CDPHE Communicable Disease Manual.

Reservoirs

Cattle are the most common reservoir for STEC, though other ruminants such as deer, elk, goats, and sheep can also carry STEC. Other animals, such as pigs, while not considered reservoirs, can be exposed to STEC in the environment and then temporarily shed the bacteria in their feces.

Modes of transmission

STEC bacteria are transmitted via the fecal-oral route through ingesting food or water that is contaminated with human or animal feces. Transmission may also occur from person to person, especially in group settings like child care centers, and from contact with infected animals and the environments they inhabit, such as petting zoos, farms, and other animal exhibits. STEC infection has also been associated with consumption of contaminated ground beef, unpasteurized apple juice and cider, unpasteurized milk and other dairy products, raw fruits and vegetables (especially leafy greens and sprouts), and uncooked flour and dried meats (e.g., jerky). The risk of transmission may be elevated during international travel, especially to regions where the bacteria is endemic. Of note, the infectious dose (the number of bacteria required to produce disease) is very low.

Incubation period

The average incubation period is about 3-4 days but can range from 1 to 10 days.

Infectious period

The disease is communicable for as long as the infected person excretes STEC bacteria in their stool, which generally begins at the onset of symptoms and lasts for a variable amount of time after diarrhea has resolved. While adults typically shed bacteria for a week or less, children may shed significantly longer — up to three weeks in about one-third of infected children and sometimes longer. Prolonged carriage is uncommon. As is the case with most enteric illnesses, people are most infectious when they have diarrhea and are usually more infectious than those who are asymptomatic.

Epidemiology

During 2023, 644 cases were reported in Colorado, with a five-year average of 499 cases per year (2019-2023). On average, about a quarter of reported STEC cases were E. coli O157. The most common non-O157 STEC serotypes reported in Colorado were O26, O103, O111, and O121. Sporadic cases of STEC infection occur throughout the year, with a peak during the summer months. In 2024, a multistate outbreak of STEC O157:H7 caused by consumption of contaminated raw onions served at a retail food establishment chain resulted in 104 confirmed cases, four cases of HUS, and one death across 14 states, including 30 cases in Colorado. Other recent foodborne outbreaks of STEC have been attributed to organic carrots, organic walnuts, and raw cheddar cheese.

In 2022, there were 16,406 STEC cases reported in the United States, with a five-year average of 14,641 cases per year (2018-2022). During this time period, 22% of STEC cases in the FoodNet catchment area were hospitalized and < 1% of cases died. Four percent of cases were outbreak-associated, and approximately 15% were acquired internationally.

For more data, see Colorado reportable disease data (Colorado data), CDC WONDER and CDC BEAM Dashboard (national data), and CDC FoodNet Fast (FoodNet catchment area data).

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Clinical criteria

An infection of variable severity characterized by diarrhea (often bloody) and/or abdominal cramps. Illness may be complicated by HUS.

Note: Some clinicians still use the term thrombotic thrombocytopenic purpura (TTP) for adults with post-diarrheal HUS.

Laboratory criteria for diagnosis

Confirmatory laboratory evidence

• Isolation of E. coli O157:H7 from a clinical specimen
  OR
• Isolation of E. coli from a clinical specimen with detection of Shiga toxin or Shiga toxin genes.

Supportive laboratory evidence

• Isolation of E. coli O157 from a clinical specimen without confirmation of H antigen, detection of Shiga toxin, or detection of Shiga toxin genes
  OR
• Identification of an elevated antibody titer against a known Shiga toxin-producing serogroup of E. coli
  OR
• Detection of Shiga toxin or Shiga toxin genes in a clinical specimen using a culture-independent diagnostic test (CIDT) and no known isolation of Shigella from a clinical specimen
  OR
• Detection of E. coli O157 or STEC/ Enterohemorrhagic E. coli (EHEC)* in a clinical specimen using a CIDT.

Note: Results that read verocytotoxin-producing E. coli (VTEC) should be reported as STEC cases into EpiTrax.

Epidemiologic linkage

• A clinically compatible illness in a person that is epidemiologically linked to a confirmed or probable case with laboratory evidence
  OR
• A clinically compatible illness in a person that is a member of a risk group as defined by public health authorities during an outbreak.

Criteria to distinguish a new case from an existing case

• A new case should be created when a positive laboratory result is received more than 180 days after the most recent positive laboratory result associated with a previously reported case in the same individual. (See formula referenced in Appendix B of the 2017 CSTE Position Statement [17-ID-10] for details on time period calculation, hierarchy of dates, and interpretation.)
  OR
• When two or more different serogroups/serotypes are identified in one or more specimens from the same individual, each serogroup/serotype should be reported as a separate case.

Case classification

Confirmed

• A person that meets the confirmatory laboratory criteria for diagnosis.

Probable

• A person with isolation of E. coli O157 from a clinical specimen without confirmation of H antigen, detection of Shiga toxin or detection of Shiga toxin genes
  OR
• A clinically compatible illness in a person with identification of an elevated antibody titer against a known Shiga toxin-producing serogroup of E. coli
  OR
• A clinically compatible illness in a person with detection of Shiga toxin or Shiga toxin genes in a clinical specimen using a CIDT and no known isolation of Shigella from a clinical specimen
  OR
• A clinically compatible illness in a person with detection of E. coli O157 or STEC/EHEC from a clinical specimen using a CIDT
  OR
• A clinically compatible illness in a person that is epidemiologically linked to a confirmed or probable case with a positive lab test
  OR
• A clinically compatible illness in a person that is a member of a risk group as defined by public health authorities during an outbreak.

Suspect

• Identification of an elevated antibody titer against a known Shiga toxin-producing serogroup of E. coli in a person with no known clinical compatibility
  OR
• Detection of Shiga toxin or Shiga toxin genes in a clinical specimen using a CIDT and no known isolation of Shigella from a clinical specimen in a person with no known clinical compatibility
  OR
• Detection of E. coli O157 or STEC/EHEC in a clinical specimen using a CIDT in a person with no known clinical compatibility
  OR
• A person with a diagnosis of post-diarrheal HUS/TTP (see HUS case definition). 

Interpretation note: Epi-linked probable cases can be epi-linked to either a confirmed or probable case, as long as the index case has a positive test result (see laboratory criteria, above). Additionally, confirmed or laboratory-confirmed probable cases can include asymptomatic infections and infections at sites other than the gastrointestinal tract that are laboratory-confirmed (rare).

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• The Colorado State Public Health Laboratory (“State Lab”) provides testing services to support public health investigations.
• The State Lab may test clinical and/or environmental samples when determined to be necessary for public health investigations. These services vary by pathogen but may include:
  • Testing for individuals who have been restricted or excluded from work or child care by public health
  • Testing for outbreak investigations, with prior approval from CDPHE
  • Other testing services as discussed with CDPHE
• The State Lab maintains a test directory, guidance for submitting samples, and other helpful resources on their webpage.
  • Additional questions can be directed to the Lab Coordinators by email (cdphe_labcoordinators@state.co.us; preferred method) or phone 303-692-3069).
• Clinical and commercial laboratories are required to submit STEC isolates or clinical material to the State Lab for confirmation and whole genome sequencing (WGS; i.e., molecular subtyping). While these submissions do not require prior approval from CDPHE, a complete lab requisition form is required for each isolate/clinical material submission to the State Lab.
  • WGS results are used for public health surveillance only and cannot be released to clinical providers or used for clinical decision-making.
  • The State Lab does not perform routine antimicrobial susceptibility testing (AST); providers interested in AST should order it from a clinical or commercial laboratory.

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Interview all confirmed and probable (including epi-linked probable) cases of STEC to determine:

• Potential source of infection, and implement disease control measures as appropriate
• If others are ill (i.e., could this be an outbreak?)
• If the case may be a source of infection for others (e.g., a high-risk worker or a diapered child), and if so, prevent further transmission

Local health departments have primary responsibility for interviews of sporadic cases in their jurisdictions. CDPHE is available to assist with case investigations upon request through CDPHE’s Enteric Disease Interview Team (EDIT). Interviews should be conducted and appropriate disease control measures implemented as soon as reasonably possible after the case is reported. Interviews should not be delayed until confirmatory laboratory testing is completed at the state public health lab.

Forms 

For single cases, use the CDPHE STEC case investigation form for your interview, and enter the information into the case’s morbidity record (CMR) in EpiTrax. Interview all cases, regardless of specimen source (stool, blood, wound, urine, etc.).

For surveillance purposes, collect exposure histories for the seven days before symptom onset. Determining the exposure period can be difficult for cases who do not have an acute onset of gastrointestinal symptoms. It’s important to do a complete assessment for GI illness, even when the specimen was collected from a source other than stool, to determine if any GI symptoms were present, even if mild. Use the following criteria to determine the case’s exposure period:

1. If the case reports diarrhea or vomiting, then use the onset date of diarrhea/vomiting to determine exposure period.
2. If the case does not report diarrhea or vomiting but reports other clinically relevant symptoms (see Clinical description section above), then use the onset date of other symptoms to determine exposure period.
3. If the case does not report onset of any clinically relevant symptoms (see Clinical description section above), then use the specimen collection date to determine exposure period.*

*Do not enter specimen collection date as “onset date” in EpiTrax (clinical tab); use this date to determine exposure period only. “Onset date” in EpiTrax only applies if the case experienced symptoms of illness. Otherwise, leave this field blank.

If the case reports international travel for even one day during their exposure period, it is fine to complete the travel section then skip to the “School, work, and volunteer information” section. No other additional exposure information needs to be collected.

After completing the case interview, enter the information into the case’s morbidity record (CMR) in EpiTrax, including the investigation form, and conduct any necessary disease control activities. If an outbreak is suspected, create a new outbreak in EpiTrax, and contact CDPHE if assistance is needed. This includes requests for additional testing at the State Lab.

Identify and evaluate contacts

Symptomatic contacts

• Contacts of a case with a positive lab test who have clinically compatible symptoms are epi-linked probable cases and are treated the same as cases with a positive lab test for disease control purposes. See Disease control measures below.
  • Complete a case interview with all epidemiologically linked probable cases.
  • Epi-linked probable cases who have been interviewed should be entered into EpiTrax as a new, probable STEC morbidity record (CMR). Link this newly created CMR to the laboratory-confirmed case’s CMR under the “contacts” tab in EpiTrax.
• Refer symptomatic individuals who have not previously been tested (especially if they are high-risk workers) to their health care provider for stool testing and appropriate medical care.
• If a common source of exposure is suspected (e.g., a shared meal or social event), create an outbreak record in EpiTrax and notify CDPHE as soon as possible.  

Asymptomatic contacts 

• Ask about high-risk occupations, including food handling, health care, community residential programs, and child care/school attendance.
• Provide information on symptom monitoring and next steps if symptoms develop.
  • Stress the importance of good handwashing, personal hygiene, excluding themselves from work, and notifying their supervisor whenever they have a diarrheal illness.
  • If an asymptomatic contact develops diarrhea, follow the steps outlined above under symptomatic contacts. If the contact works in a high-risk setting, exclude them from work per the Managing special situations section below, even in the absence of a positive lab test.

Reported incidence is higher than usual/outbreak suspected

If the number of reported cases of STEC in your jurisdiction is higher than usual, or if an outbreak is suspected, investigate the situation to determine the source of infection and mode of transmission. Notify CDPHE as soon as possible to discuss potential stool testing of untested, symptomatic contacts, and enter the outbreak into EpiTrax. CDPHE staff can assist local public health agencies to investigate outbreaks and determine disease control recommendations to prevent further cases, as well as coordinate surveillance of cases that cross county lines.

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E. coli (Escherichia coli) | CDC

Treatment

Antibiotics are generally not indicated for treatment of STEC because they may increase the risk of developing HUS. Antimotility agents should not be administered to cases with inflammatory or bloody diarrhea. Careful follow-up of patients with hemorrhagic colitis is recommended to detect changes suggestive of HUS.

In general, individuals experiencing diarrhea are at risk of dehydration due to loss of fluids. If symptoms persist, worsen, or are severe, cases should promptly seek medical care.

Prophylaxis

No prophylactic treatment of close contacts is recommended.

Education

Encourage the case to:

• Avoid preparing food for other individuals until diarrhea has resolved.
• Always wash hands thoroughly with soap and water for at least 20 seconds before eating or preparing food, after using the toilet, after changing diapers, and after touching pets or other animals (especially farm animals and cattle).
• After changing diapers, wash your hands and the child’s hands for at least 20 seconds. Clean and sanitize diaper changing stations/areas often.
  • In child care and other institutional settings, dispose of stool and soiled diapers/linens in a sanitary manner.
• Keep food that will be eaten raw, such as fruits and vegetables, from becoming contaminated by raw, animal-derived food products (e.g., raw meat, fish, poultry) by cleaning or using different knives and cutting boards during preparation. Store raw, animal-derived foods away from other foods that will be eaten raw while in the refrigerator.
• Thoroughly cook all food products from animals, and avoid consuming unpasteurized milk or other unpasteurized products such as juices and unpasteurized apple cider.
• Cook all ground beef, hamburger, and needle-tenderized beef products thoroughly to an internal temperature of at least 160° F.
• If served an undercooked hamburger or other ground beef product in a restaurant, send it back for further cooking.

Managing special situations 

When return to work/ child care testing is indicated, the tests (either ordered through a clinical lab or the State Lab) must either be PCR or culture-based; enzyme immunoassay (EIA) tests are not an acceptable test type for return to work/child care testing. CDPHE can help you interpret test type and/or test results upon request.

Food handlers 

When a known or suspected case of STEC occurs in a food handler, immediate involvement of public health authorities is critical.

• Definitions
  • "Exclude" means to prevent a person from working as an employee in a food establishment or entering a food establishment as an employee.
  • “Highly Susceptible Population” means people who are more likely than other people in the general population to experience foodborne disease — because they are immunocompromised, preschool-age children, or older adults — and they obtain food at a facility that provides services such as custodial care, health care, assisted living, child or adult day care center, kidney dialysis center, hospital, long-term care facility  or nursing home, or nutritional or socialization services such as a senior center.
  • “Restricted duties" means to limit the activities of an employee so that there is no risk of transmitting a disease that is transmissible through food, and the food employee does not work with exposed food, clean equipment, utensils, linens, or unwrapped single-service or single-use articles.
• Food handlers who work in a food establishment predominantly serving a highly susceptible population must remain excluded until:
  • (A) Diarrhea has resolved for at least 24 hours without the use of anti-diarrheal medications
    AND
  • (B) Adequate hygiene can be maintained, ideally as verified by environmental health
    AND
  • (C) They have two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/child care testing.
  • Include your local environmental health specialist to determine if a facility is serving a highly susceptible population.
• Food handlers who work in an establishment not predominantly serving a highly susceptible population may return to work for restricted duties while doing return to work/child care testing if:
  • (A) At least 24 hours has passed since diarrhea resolved without the use of anti-diarrheal medications 
    AND
  • (B) Environmental health specialists and the case’s employer believe working with restricted duties is feasible.
    • If either Environmental Health or the employer do not believe working with restricted duties is feasible, follow the instructions for food handlers who work in a food establishment predominantly serving a highly susceptible population (above).
  • The case may only return to regular (non-restricted duties) once they have two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/child care testing
• Additional details:
  • If the case’s confirmatory culture at the State Lab is negative, that negative counts as the first negative test to return to work.
  • A letter or memo should be sent to the food service facility documenting the requirements for the infected food handler (e.g., restricted duties, exclusion from facility). Letter templates can be requested from CDPHE.
  • Return to work testing is required even if the case was asymptomatic, or symptoms have since resolved.
  • During an outbreak, exclusion periods may be extended, additional testing may be required, and/or restricted duties may not be permitted.
• The Colorado Retail Food Establishment Regulations may require additional restrictions or disease control measures for the case, their close contacts, and/or their employer.
  • Consult with environmental health to determine if the case’s place of employment should enact additional disease control measures to be in compliance with the regulations.

Child care centers/preschools

When a case of STEC occurs in a child care center attendee or worker, immediate involvement of public health authorities is critical. 

Refer child care providers to the CDPHE Infectious Diseases in Child Care and School Settings for an overview of STEC infections.

Children

• Children with STEC must be excluded from the child care center until the following criteria have been met:

• Return to child care testing is required (as described above), even if the case was asymptomatic or symptoms have since resolved.
  • If the case’s confirmatory culture at the State Lab is negative, that negative counts as the first negative test to return to child care.
• Parents of cases should be counseled not to take their children to another child care center during this period of exclusion in order to avoid possible transmission of STEC at a new location.
• Determine whether additional children or staff are (or have recently been) ill with diarrheal illness.
  • Other children or staff with diarrhea must be excluded and referred to their health care provider for stool testing and appropriate medical care.
  • If other cases in the center are identified, initiate an outbreak investigation, and consider sending a letter home to parents. Contact CDPHE for assistance.
  • If the case is the only person in the classroom or facility who has been ill, no further action is indicated for other children/staff in that classroom or center.
• Reinforce the importance of meticulous handwashing, proper sanitizing and disinfection, and proper diaper-changing technique with child care center staff. If possible, this should be verified by environmental health.
• Consult with CDPHE for instances in which children attend drop-in style care at gyms, churches, etc.

Staff

• Since many child care center staff assist with food preparation and/or feeding children, those with STEC infection must be excluded from work until
  • (A) At least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications 
    AND
  • (B) They have two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing.
  • In this situation, it is important for Environmental Health staff to work closely with the center to ensure that affected staff are excluded until cleared by public health. See section Food handlers above.
  • Return to work testing is required, even if the case was asymptomatic or symptoms have since resolved.
    • If the case’s confirmatory culture at the State Lab is negative, that negative counts as the first negative test to return to work.
• Staff with no role in food preparation or feeding (e.g., office staff) may return to work after diarrhea has been resolved for at least 24 hours without the use of anti-diarrheal medications. Return to work testing will not be required for these workers.
• Determine whether additional children or staff are (or have recently been) ill with diarrheal illness.
  • Other children or staff with diarrhea must be excluded and referred to their health care provider for stool testing and appropriate medical care.
  • If other cases in the center are identified, initiate an outbreak investigation, and consider sending a letter home to parents. Contact CDPHE for assistance.
  • If the case is the only person in the classroom or facility who has been ill, no further action is indicated for other children/staff in that classroom or center.
• Reinforce the importance of meticulous handwashing, proper sanitizing and disinfection, and proper diaper-changing technique with child care center staff. If possible, this should be verified by environmental health.

Schools 

Refer school personnel to the CDPHE Infectious Diseases in Child Care and School Settings for an overview of STEC infections. 

• Students or staff with STEC must be excluded until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications.
• Nursing staff or other school staff that provide medical care or administer medications must be excluded until
  • (A) At least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications 
    AND
  • (B) They have two consecutive negative stool tests collected at least 24 hours apart at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing. See section Patients and staff in health care facilities below.
• Students or staff who handle/prepare food for others must not prepare food until
  • (A) At least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications 
    AND
  • (B) They have two consecutive negative stool tests obtained at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing. See section Food handlers above.
• In the above two scenarios, return to work/school testing is required, even if the case was asymptomatic or symptoms have since resolved.
• If there are concerns about the case’s hygiene (e.g., the case has developmental disabilities and wears diapers), consider obtaining two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given, before a case returns to school. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing.
• During an outbreak, exclusion may be lengthened and additional testing may be required.

Community residential programs (including facilities serving the developmentally disabled)

Actions taken in response to a case of STEC in a community residential program will depend on the type of program and the level of functioning of the residents. In general: 

• Residents with STEC must be placed on contact precautions until
  • (A) At least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications 
    AND
  • (B) They have two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing.
• Residents and staff with STEC must be excluded from handling or preparing food for other residents until
  • (A) At least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications 
    AND
  • (B) They have two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing.
• For staff members who provide direct patient care (e.g., feed patients, give mouth or denture care, or give medications), follow guidelines for staff in health care facilities below.
• In these scenarios, return to work testing is required, even if the case was asymptomatic or symptoms have since resolved.
• Staff members with STEC infection who are not food handlers and do not provide direct patient care must be excluded from work until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. Return to work testing is not required for these workers.
• During an outbreak, exclusion may be lengthened and additional testing may be required.

Patients and staff in health care facilities (including hospitals, medical and dental clinics, skilled nursing and long-term care facilities)

Hospitals and skilled nursing and long-term care facilities may have written infection control policies and procedures for handling cases of communicable disease among patients and staff members. 

If a facility’s policies are more strict than the guidance below, they can follow those. Otherwise:

• Patients with STEC must be placed on contact precautions until
  • (A) At least 24 hours after their diarrhea resolves 
    AND
  • (B) They have two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing.
• Health care workers who provide direct patient care or handle medications (e.g., pharmacists) must be excluded from work until
  • (A) At least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications
    AND
  • (B) They have two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing.
  • Return to work testing is required, even if the case was asymptomatic or symptoms have since resolved.
  • If the case’s confirmatory culture at the State Lab is negative, that negative counts as the first negative test to return to providing direct patient care.
• Health care workers who do not provide direct patient care can return at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. Return to work testing is not required for these workers.
• Depending on the type of health care facility, it may be possible for a health care worker who normally does direct patient care to return to work for restricted duties while doing return to work testing if:
  • (A) At least 24 hours has passed since after diarrhea has resolved without the use of anti-diarrheal medications
    AND
  • (B) The case’s employer believes working with restricted duties is feasible.
  • They may only return to regular (non-restricted duties) once they have two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. Only PCR or culture-based tests are acceptable; EIA tests cannot be used for return to work/childcare testing.
    • “Restricted duties" means to limit the activities of the health care worker so that there is no risk of passing on a disease that is transmissible through direct patient care or the handling of medications. Specifically, the health care worker does not put hands directly on a patient, including but not limited to: taking vitals, performing an exam, or administering vaccinations or handling medications or clean equipment that will be used by staff or patients.
    • Examples of restricted duties may include:
      • Checking patients in at the front desk
      • Calling patients to share lab results
      • A pharmacist handling only sealed packaged/bottled medications, but not compounding medication/administering vaccines/counting pills
• A letter or memo should be sent to the health care facility documenting the requirements for the infected health care worker (e.g., restricted duties, exclusion from facility). Letter templates can be requested from CDPHE.

Environmental measures

• Implicated food items and food prepared by cases must be removed from the environment.
• A decision about testing suspect/implicated food items must be made in consultation with CDPHE.
  • The general policy of the State Lab and the Communicable Disease Branch is only to test food samples associated with outbreaks, not in single cases.
• If a commercial product is suspected, CDPHE Communicable Disease Branch will coordinate follow-up with the CDPHE Division of Environmental Health and Sustainability and relevant outside agencies.

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American Academy of Pediatrics. Red Book: 2024-2027 Report of the Committee on Infectious Diseases, 33rd Edition. Illinois, Academy of Pediatrics, 2024.  

CDC Website: www.cdc.gov (click on “Diseases and Conditions”) 

Centers for Disease Control and Prevention (CDC). FoodNet Fast: Pathogen Surveillance Tool. Atlanta, Georgia: U.S. Department of Health and Human Services. Available from URL: http://wwwn.cdc.gov/foodnetfast. Accessed May 21, 2025.

Centers for Disease Control and Prevention. National Notifiable Diseases Surveillance System (NNDSS) Annual Summary Data for years 2016-2022, United States, CDC WONDER online database. Accessed at http://wonder.cdc.gov/nndss-annual-summary.html on May 22, 2025.

Heymann DL, ed. Control of Communicable Diseases Manual, 21st Edition. Washington, DC, American Public Health Association, 2022.

Hoffman RE, Shillam PJ. The use of hygiene, cohorting, and antimicrobial therapy to control an outbreak of STEC . Am J Diseases Children. 1990;144:219-221.

Nelson JD, Kusmiesz, H, Jackson LH, Woodman E. Trimethoprim-sulfamethoxazole therapy for STEC . JAMA. 1976;235:1239-1243.

Shiga Toxin-producing Escherichia coli (STEC) 2018 Case Definition | CDC. (n.d.). https://ndc.services.cdc.gov/case-definitions/shiga-toxin-producing-escherichia-coli-2018/

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CDPHE Communicable Disease Branch

• Phone: 303-692-2700 or 800-866-2759
• Fax: 303-782-0338
• After hours: 303-370-9395

CDPHE Lab Coordinators: 

• Email (preferred): cdphe_labcoordinators@state.co.us  
• Phone: 303-692-3069

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