A genus of bacteria which includes the causative organism of plague, Yersinia pestis. It also includes Yersinia enterocolitica, an uncommon cause of fever, abdominal pain and bloody diarrhoea in children which may last from 1-3 weeks. Occasionally the child also develops a skin rash and joint pains. Treatment is with antibiotics. Adults with this infection give a picture more like appendicitis, with right sided abdominal pain.