Cause: Bacterium Yersinia pestis

Illness and treatment: Plague causes three main syndromes: bubonic (fever, headache, nausea and unilateral lymph node swelling); septicemic (bacteremia and multi-organ system failure); and pneumonic (pneumonia). A patient may have several syndromes. About 11% of plague cases in the United States are fatal. Treatment is with antibiotics and supportive care.

Sources: Wild rodent populations are the natural reservoir where plague is maintained by fleas. Humans are infected through flea bites, handling tissues from infected animals, or respiratory droplet spread from animals or people with pneumonic plague.

Prevention: Avoid contact with sick or dead wild animals, rodent-proof houses, prevent pets from contracting fleas, and use repellents on skin and clothing when outdoors.

Recent Washington trends: Serologic sampling of 8,921 wild carnivores collected between 1975 and 2015 in Washington showed 2.5% seropositivity. Only one animal has tested positive since 2003. The majority of animals tested in recent years were from the Yakama Nation Wildlife Department. Other surveillance partners include the Department of Fish and Wildlife's licensed nuisance trappers, the Makah Tribe Forestry-Wildlife Division, and Joint Base Lewis-McChord Yakima Training Center. Human infections are rare: the last reported case was an animal trapper in Yakima exposed while skinning a bobcat in 1984. In neighboring Oregon, 1 person living in the southern part of the state was diagnosed with plague in 2015.

Purpose of Reporting and Surveillance

  • To assist in the diagnosis and treatment of cases
  • To identify potentially exposed close contacts, health care workers and laboratory personnel and to provide counseling
  • To identify sources of transmission (e.g., wild rodents or other animals) and to prevent further transmission from such sources

Legal Reporting Requirements

  • Health care providers and Health care facilities: Immediately notifiable to local health jurisdiction.
  • Laboratories: immediately notifiable to local health jurisdiction; submission required – presumptive positive isolate or if no isolate specimen associated with presumptive positive result, within 2 business days.
  • Veterinarians: animal cases notifiable to Washington State Department of Agriculture (see:
  • Local health jurisdictions: Suspected and confirmed cases are immediately notifiable to the Washington State Department of Health (DOH) Communicable Disease Epidemiology (CDE) (1-877-539-4344). 

More Resources

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