Non-pestis Yersiniosis
2025 Case Definition

Background

Yersinia spp. are facultative anaerobic Gram-negative coccobacilli. In the U.S., the most common cause of non-pestis yersiniosis is Y. enterocolitica, an intestinal and oropharyngeal commensal bacterium in pigs.¹ Infections are commonly attributed to the handling or consumption of raw or undercooked contaminated pork but can also be acquired from other contaminated foods (e.g., tofu, produce, and milk), the feces of other animals (e.g., rodents, cows, sheep, horses, dogs, and cats), water, or (rarely) the feces of an infected person.^1-7 Young children (<5 years old) and older adults (≥65 years) are at highest risk of infection, with average annual incidence during 2010–2022 of 1.43 and 1.75 cases per 100,000 age-specific population, respectively.⁸

The incubation period for non-pestis yersiniosis is typically 4-6 days (range, 1-14 days).¹ Clinical manifestations include fever, diarrhea (potentially bloody), and abdominal pain due to inflamed lymph nodes (mesenteric adenitis); abdominal pain can be severe enough to mimic appendicitis. Extra-intestinal manifestations can include soft tissue abscesses, sepsis, and post-infectious immune-mediated syndromes such as reactive arthritis and soft tissue swellings (erythema nodosum). Sepsis has been reported after transfusion with red blood cells contaminated with Y. enterocolitica. People with iron overload (e.g., hemochromatosis) or underlying immunosuppression are particularly susceptible to septicemia. Although rare, invasive infections can be fatal.

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

Note: The categorical labels used here to stratify laboratory evidence are intended to support the standardization of case classifications for public health surveillance. The categorical labels should not be used to interpret the utility or validity of any laboratory test methodology. 

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.

Probable

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

Confirmed

• Meets the confirmatory laboratory evidence.