Plague

Yersinia pestis is the causative organism of plague, an enzootic vector-borne disease usually infecting rodents (e.g., rats) and fleas. Over the past 2,000 years, three devastating pandemics have occurred. Plague pandemics have caused social and economic [Page 812]devastations on a scale unmatched by any other infectious disease except for smallpox. Although at the present time the organism is not considered a major health concern, approximately 2,500 cases annually are reported worldwide, and recently the World Health Organization categorized plague as a reemerging infectious disease. Despite major advances in diagnosis and treatment that were made since the discovery of the causative organism, the disease persists in several parts of the world, causing significant recurrent outbreaks in rodents and humans.