Yersiniosis is a disease of man and other animals due to Yersinia pseudotuberculosis (syn. Pasteurella pseudotuberculosis) and Y. enterocolitica. The majority of human and animal infections have been recorded in Europe, but in recent years the disease has been recognized more frequently in North America, Asia and Australia. In the United Kingdom Y. pseudotuberculosis infection has been found in 6 species of wild mammals and in 21 species of wild birds. Principal reservoirs of infection are rodents and birds. Human infection with Y. pseudotuberculosis is probably acquired by direct or indirect contact with animals. Yersinia enterocolitica infection is less widespread in wild animals but more prevalent in human beings than the corresponding Y. pseudotuberculosis infection. Its epidemiology remains obscure.