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Plague is caused by infection with the bacterium Yersinia pestis, found in rodents and their fleas in many areas of the world, including the United States. Human plague in the western United States occurs sporadically. Plague is a potential agent of biological terrorism. One case of pneumonic plague without travel to an endemic area may indicate an act of terrorism and constitutes a potential public health emergency.


Resources for the general public

Resources for health care professionals

Plague in King County

Purpose of surveillance:

  • To investigate cases caused by potential agents of bioterrorism
  • To identify naturally occurring sources of infection
  • To confirm reported cases and to ensure that exposed persons receive post-exposure prophylaxis and/or monitoring

Local epidemiology:

Since 1907, only one case of human plague has been reported in Washington state in an animal trapper with bubonic plague reported in 1984.