Yersiniosis

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

• 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

• Individual cases of yersiniosis are only reportable within the following seven counties: Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson.
  • Outbreaks of yersiniosis are reportable statewide. 
• All specimens with a positive test for Yersinia (non-pestis species; 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 Yersinia (non-pestis species) 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.

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

Yersiniosis refers to disease caused by Yersinia enterocolitica (most common) or Yersinia pseudotuberculosis bacteria. The species of Yersinia that cause enteric illness are different from Yersinia pestis, which causes plague, a reportable zoonotic disease. 

Clinical description

The most common symptoms of yersiniosis are abdominal pain, fever, and diarrhea, which may be bloody. Less commonly, skin rash, joint pains, or a blood infection may occur. Infections in older children and adults can mimic acute appendicitis with right-sided abdominal pain, tenderness of the abdomen, and fever. Patients with acute yersiniosis may also report pharyngitis, which is atypical of other causes of bacterial diarrhea/gastroenteritis. Asymptomatic infections may occur.

Extra-intestinal manifestations may be present, such as sepsis, wound and soft tissue infections (including abscesses), or pharyngitis. Gastrointestinal symptoms may be absent in these instances. Reactive arthritis and erythema nodosum are commonly reported complications following acute yersiniosis. These conditions are often immunologic phenomena associated with Yersinia infection and certain host factors.

Reservoirs

Animals are the primary reservoir for Yersinia bacteria. Pigs are the primary reservoir for Y. enterocolitica and asymptomatic carriage of the bacteria in pigs is common in winter. Y. enterocolitica has also been recovered from water. Y. pseudotuberculosis has numerous animal reservoirs, including birds, rodents, rabbits, deer, dogs, cats, and cattle. 

Modes of transmission

Yersinia bacteria are transmitted via the fecal-oral route. The most common mode of transmission is by consuming or handling contaminated food or water, most often raw or undercooked pork (specifically pork intestines, or chitterlings/chitlins). Transmission may also occur by consuming raw milk, raw milk products, or untreated water. However, any food contaminated with the bacteria can be a source of infection and outbreaks have involved tofu made with contaminated water and pasteurized milk that was contaminated after pasteurization. In addition, farm animals and pets, such as puppies and kittens with diarrhea, can be sources of human infection. Person-to-person spread appears to be rare but can occur. 

Incubation period

The average incubation period is 4-6 days (range 1-14 days).

Infectious period

Secondary transmission is thought to be rare. However, an infected person can shed the bacteria in their stool up to six weeks after onset of illness, or as long as 2-3 months if untreated. Both children and adults have been reported with prolonged asymptomatic carriage. 

Epidemiology

During 2023, 141 cases were reported in Colorado’s seven-county surveillance area (Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson), with a five-year average of 82 cases per year (2019-2023). Cases are reported throughout the year, peaking during the spring and summer. Most reported cases are isolated, sporadic cases not associated with outbreaks.

In 2022, 1,003 yersiniosis cases were reported in the FoodNet catchment area of the United States, with a five-year average of 623 cases per year (2018-2022). Twenty-two percent of these cases were hospitalized, and < 1% died. Fewer than 1% of cases were associated with outbreaks, and 4% were associated with international travel.

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

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Clinical criteria

A person with a clinically compatible illness. Common presentations of illness include fever (measured or subjective), diarrhea (bloody or non-bloody), or abdominal pain that may be severe enough to mimic appendicitis. However, presentations of extraintestinal illness can include sepsis, wound infection, or soft tissue infections, and gastrointestinal signs may be absent in these instances.

Note: Post-infectious, immune-mediated syndromes such as reactive arthritis and erythema nodosum are not directly caused by the infection and are not included as part of the clinical criteria.

Laboratory criteria

Confirmatory laboratory evidence:

• Isolation of any non-pestis Yersinia spp. by culture from a clinical specimen

Presumptive laboratory evidence:

• Detection of any non-pestis Yersinia spp. in a clinical specimen (e.g., stool or blood specimen) using a Nucleic Acid Amplification Test (NAAT) or other molecular testing method

Epidemiologic linkage

A person who shares an exposure with (or is exposed to) a confirmed or probable case of non-pestis yersiniosis.

Criteria to distinguish a new case from an existing case

A new case should be enumerated when:

• A repeat culture, NAAT, or other molecular test result more than 365 days of initial report (e.g., specimen collection date) should be enumerated as a new case for surveillance.
• When two or more non-pestis Yersinia spp. are detected from one or more specimens from the same individual, each identified Yersinia spp. should be enumerated as a separate case.

Case classification

Confirmed

• Meets the confirmatory laboratory evidence

Probable

• Meets the presumptive laboratory evidence, OR 
• Meets clinical criteria AND epidemiologic linkage criteria

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 in Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson counties are required to submit Yersinia 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 yersiniosis within the seven-county surveillance area (Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson) 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 Lab.

Forms 

For single cases, use the CDPHE Yersiniosis 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 laboratory-confirmed cases for disease control purposes. See Disease control measures below. 
  • Complete a case interview with all epidemiologically linked probable cases.
    • Individual cases of yersiniosis are only reportable in Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson counties (and should be entered into EpiTrax).
  • Notify CDPHE if there are multiple symptomatic contacts of a case, regardless of which county they reside in.
• 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 hand washing, 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 yersiniosis 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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Yersinia (non-pestis) (Yersiniosis) | CDC

Treatment

Most people infected with Yersinia do not require antibiotic treatment. Yersinia organisms are generally resistant to penicillin, ampicillin, and first generation cephalosporins. In more severe or invasive cases, antibiotics such as aminoglycosides, doxycycline, trimethoprim-sulfamethoxazole, and ciprofloxacin may be used.

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. 
• 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, especially pork, and avoid consuming unpasteurized milk or other unpasteurized products. 
• After handling raw chitlins, clean hands and fingernails thoroughly with soap and water before touching infants or their toys, bottles, or pacifiers. Someone other than the person handling food should care for children while chitlins are being prepared.

Managing special situations

Food handlers 

• Food handlers with yersiniosis must be excluded from work until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications and adequate hygiene can be maintained, ideally as verified by environmental health. "Exclude" means to prevent a person from working as an employee in a food establishment or entering a food establishment as an employee. 
  • While individual circumstances may vary, cases are generally not required to provide two consecutive negative stool tests to return to work. 
  • If a case has questionable hygienic practices or there are other concerns, consider excluding the case from work until the case has obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given.
• In an outbreak situation, longer exclusion and/or return to work testing may be required to return to food handling.
• 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

• Children or staff with yersiniosis should be excluded until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications. 
  • 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 yersiniosis at a new location.
  • Since many child care center staff assist with food preparation and/or feeding children, it is very important that staff with Yersinia infection follow this guidance. See Disease control measures section (Food handlers) above.
  • If there are concerns about hygienic practices at the child care center, consider excluding the case from care until the case has obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given.
• Determine whether additional children or staff are (or have recently been) ill with diarrheal illness.
  • Other children or staff with diarrhea should 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. 
    • In an outbreak situation, longer exclusion and/or return to work/child care testing may be required. 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 hand washing, 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.

Schools 

• Students or staff with yersiniosis should be excluded until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications.
  • 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.
• Students or staff who handle food for others must not prepare food until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. See Disease control measures section (Food handlers) above. 
• In an outbreak situation, longer exclusion and/or return to work/school testing may be required.

Community residential programs (including facilities serving the developmentally disabled)

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

• Staff members with yersiniosis should be excluded from work until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. 
  • 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. 
• While individual circumstances may vary, in general, staff members are not required to provide two negative stool tests to return to work. 
• Residents with yersiniosis should be placed on contact precautions until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications.
  • If the resident has questionable hygiene, is incontinent, or there are other concerns, the resident should remain on contact precautions until they have obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given. 
• Residents and staff with yersiniosis must be excluded from handling or preparing food for others until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. See Disease control measures section (Food handlers) above. 
• In an outbreak situation, longer exclusion and/or return to work 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/long-term care facilities generally have written infection control policies and procedures for handling cases of communicable disease among patients and staff members. 

If a facility does not have such policies in place, provide the following recommendations: 

• Health care workers with yersiniosis who provide direct patient care or handle medications (e.g., pharmacists) should be excluded from work until at least 24 hours after diarrhea has resolved without the use of anti-diarrheal medications.
  • While individual circumstances may vary, in general, health care workers are not required to provide two negative stool tests to return to work. 
• Patients with yersiniosis should be placed on contact precautions until at least 24 hours after their diarrhea has resolved without the use of anti-diarrheal medications. 
  • If the patient has questionable hygiene, is incontinent, or there are other concerns, the patient should remain on contact precautions until they have obtained two consecutive negative stool tests collected at least 24 hours apart and at least 48 hours after completion of antibiotics, if antibiotics are given.  
• In an outbreak situation, longer exclusion and/or return to work testing may be required.

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.  

Aziz, M., & Yelamanchili, V. S. (2023b, July 3). Yersinia enterocolitica. StatPearls - NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK499837/

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 05/16/2025.

Clinical overview of Yersiniosis. (2024, April 25). Yersinia Infection (Yersiniosis). https://www.cdc.gov/yersinia/hcp/clinical-overview/index.html

Heymann DL, ed. Control of Communicable Diseases Manual, 21st Edition. Washington, DC, American Public Health Association, 2022.
Non-pestis Yersiniosis 2025 Case Definition | CDC. (n.d.-b). https://ndc.services.cdc.gov/case-definitions/non-pestis-yersiniosis/

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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 Laboratory Coordinators

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

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