INTRODUCTION

Yersinia genus includes several species. The most important for human disease are Yersinia enterocolitica, Yersinia pseudotuberculosis, and Y. pseudotuberculosis subspecies pestis. More commonly Y. pseudotuberculosis subspecies pestis is listed as Yersinia pestis. Yersinia pseudotuberculosis and Y. pestis are clearly closely related species by analysis of the genome. However, Y. enterocolitica and Y. pseudotuberculosis produce clinically similar disease and both are quite distinct from that produced by subspecies Y. pestis; hence, in this chapter the older terminology Y. pestis will be used, and Y. enterocolitica and Y. pseudotuberculosis discussed separately.

YERSINIA PESTIS

The well-known unfortunate events of September 11, 2001, have produced a resurgence in interest in an ancient organism. Additionally, Y. pestis has been classified as a re-emerging pathogen. Yersinia pestis was first identified by Alexander Yersin in 1894 during an outbreak in Hong Kong. Yersinia pestis is typically a zoonosis with human infection an incidental event. Domestic dogs and cats can also transmit the disease to humans. The disease is variably distributed throughout the world. Its distribution in the United States is largely limited to the west, particularly New Mexico, Arizona, and California.