Besides Yersinia pestis (see plague) the Yersinia group of bacteria also includes two species frequently causing illness (mainly enteritis) in humans; Yersinia enterocolitica and Yersinia pseudotuberculosis.

Both are zoonoses, with a large number of animals, but mainly pigs, acting as reservoirs. Raw/undercooked meat consumption is often the cause of infection in humans. Direct transmission from other animals (e.g. pets) or through contaminated food or drink is also possible.

After an incubation period of 3–7 days, the clinical presentation includes fever, diarrhoea and abdominal pain in the right lower part of the abdomen, mimicking appendicitis. Both infections respond well to antibiotics, but untreated symptoms of abdominal pain may last for a long while. Children and adolescents are most affected. Other manifestations such as joint inflammation, “erythema nodosum” (a skin affection) and Reiter’s syndrome (inflammation of eyes and joints) can also appear.

Outbreaks are sometimes detected as a sudden increase in appendectomies due to mistaken diagnoses of appendicitis. Prophylactic measures include adequate hygiene in meat processing (especially of pork), hand hygiene and protection of water supplies.