Plague Overview

• Plague is an acute and potentially fatal bacterial infection that affects humans and most mammals. It is caused by Yersinia pestis, a Gram-negative, bipolar-staining, pleomorphic coccobacillus.
• A bioterrorism-related release of Y. pestis could result in the infection of not only humans but also domestic and peri-domestic animals via:
  • inhalation of the primary aerosol,
  • ingestion of food or water exposed to the primary aerosol,
  • ingestion of another infected animal, or
  • flea bite from an infective flea (that had previously fed on a bacteremic animal).
• Natural transmission cycles involving wild rodents and their fleas can be found in many regions of the western United States.
• Occasionally, naturally occurring plague causes widespread outbreaks or epizootics among rodent populations.
• While it appears that virtually any mammal can be infected with plague bacteria, some species do not develop clinical signs of illness following infection and are unlikely to pose great risks to humans.