Yersinia
Yersinia enterocolitica, Yersinia pseudotuberculosis
Occurrence
Enteric yersiniosis occurs worldwide. Y. enterocolitica is widespread in the environment and among animal populations, primarily in pigs and, less commonly, in dairy cows. Y. enterocolitica is also found in wild animals. Y. pseudotuberculosis is mainly found in the environment. Similar to Listeria, Y. enterocolitica can also multiply on contaminated food in the fridge.
Infection route
Yersiniosis is usually caused faecal-orally by consumption of contaminated food and water, especially raw or medium-cooked pork and raw or inappropriately heated dairy products. The bacteria can also multiply at 4 °C (e.g. refrigerator). In major foodborne Y. pseudotuberculosis outbreaks in the EU, contaminated vegetables (bean sprouts, tofu), water and milk have been confirmed as vehicles of infection. Transmission can also occur through contaminated blood supplies. Direct transmission from infectious animals and humans is rare.
Symptoms
In children, the disease usually manifests itself with gastrointestinal symptoms, whereas adults may show signs of appendicitis (pseudo-appendicitis). The classic symptoms are diarrhea, fever, and severe abdominal pain (untreated for a duration of 1-3 weeks). The diarrhea may be watery but also bloody; after a few days, joint pain, joint inflammation and skin changes may also occur. In rare cases, the so-called Reiter syndrome (arthritis, urethritis, conjunctivitis) may develop.
In pigs, which are considered to be the main reservoir for Y. enterocolitica, bloody diarrhoea may occur in individual cases, and joint and lung inflammation can be found in young animals. In most cases, however, infections remain asymptomatic and unnoticed by the animal owner.
Human
In 2025, 202 first-time isolates of Yersinia spp. were sent to the National Reference Centre for Yersinia. Of these, 89 isolates were found to be pathogenic; 88 of these were identified as Y. enterocolitica and one as Y. pseudotuberculosis. The incidence of yersiniosis cases confirmed by culture at the Reference Centre stood at 0.97 per 100,000 inhabitants in 2025. A total of 84 cases were reported to the Epidemiological Reporting System (EMS) (as at 24 February 2026).
Specialist Information on Human Medicine
Yersinia are facultative anaerobes (i.e. capable of growing even in the absence of oxygen), pleomorphic, Gram-negative (staining red in Gram staining) rods belonging to the family Enterobacteriaceae. As psychrophilic (= cold-loving) bacteria, they can be cultured at temperatures between 4 °C and 42 °C. They are commonly found in temperate climates.
The genus Yersinia comprises 14 species, of which enteropathogenic Yersinia (Y. enterocolitica and Y. pseudotuberculosis) are obligate pathogenic microorganisms of clinical significance in human medicine.
In 2025, typing of the 88 Y. enterocolitica isolates at the National Reference Centre for Yersiniosis revealed 78 cases of biovar 4/O:3 (89 per cent) and 10 cases of serovar 2/O:9 (11 per cent). In recent years, the disease has been most common in the 0 to 14 age group.
Diagnosis
A purely symptomatic diagnosis based solely on the clinical presentation is very difficult to make. Culturing the bacteria from stool samples is the method of choice, also for determining serotypes and biotypes. Furthermore, blood, cerebrospinal fluid, puncture fluid, lymph node aspirate or peritoneal fluid may also be used. In untreated patients, the bacteria may continue to be excreted in the stool for weeks even after clinical symptoms have subsided. Molecular biological methods, such as PCR testing, are also available for detecting the pathogen.
Symptoms
The infections caused – known as yersiniosis – present with a wide range of symptoms.
In infants and young children, the most common presentation is a self-limiting, acute gastroenteritis with vomiting, watery to bloody diarrhoea and fever. The illness can last for one to two weeks.
In school-age children and adolescents, the infections usually take the form of acute mesenteric lymphadenitis (inflammatory swelling of the abdominal lymph nodes) accompanied by abdominal pain. The clinical presentation may resemble appendicitis (= inflammation of the appendix) (‘pseudo-appendicitis’).
In adults, various clinical forms occur, such as flu-like infections with pharyngitis (= inflammation of the throat), myalgia (= muscle pain) and fever, or ileocolitis (= inflammation of the large intestine and parts of the small intestine) involving the mesenteric lymph nodes (“pseudocrohn”).
Yersiniosis may be associated with concomitant or secondary symptoms: reactive arthritis, erythema nodosum (= acute inflammation of the subcutaneous fatty tissue), arthralgia (= joint pain) or myalgia (= muscle pain). Y. enterocolitica tends to cause a gastroenteritic clinical picture, whilst Y. pseudotuberculosis more frequently leads to pseudo-appendicitis.
Contact
Stefanie Klatovsky, MSc
- stefanie.klatovsky@ages.at
- +43 50 555 61210
-
Beethovenstraße 6
8010 Graz
Dr. Christian Kornschober
- christian.kornschober@ages.at
- +43 50 555 61201
-
Beethovenstraße 6
8010 Graz
Last updated: 11.08.2026
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