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NOTE: A surveillance case definition is a set of uniform criteria used to define a disease for public health surveillance. Surveillance case definitions enable public health officials to classify and count cases consistently across reporting jurisdictions. Surveillance case definitions are not intended to be used by healthcare providers for making a clinical diagnosis or determining how to meet an individual patient’s health needs.

Clinical Description

A disease characterized by fever and leukocytosis that presents in one or more of the following principal clinical forms:

  • Regional lymphadenitis (bubonic plague)
  • Septicemia without an evident bubo (septicemic plague)
  • Plague pneumonia, resulting from hematogenous spread in bubonic or septicemic cases (secondary plague pneumonia ) or inhalation of infectious droplets (primary plague pneumonia)
  • Pharyngitis and cervical lymphadenitis resulting from exposure to larger infectious droplets or ingestion of infected tissues (pharyngeal plague)
  • Plague is transmitted to humans by fleas or by direct exposure to infected tissues or respiratory droplets.

Laboratory Criteria For Diagnosis

  • Isolation of Yersinia pestis from a clinical specimen, OR
  • Fourfold or greater change in serum antibody to Y. pestis

Case Classification


A clinically compatible illness with supportive laboratory results (demonstration of a single serologic test result suggestive of recent infection with no history of immunization, or demonstration of a Fraction I antigen in blood, bubo aspirate, or tissue by antigen detection -- enzyme-linked immunosorbent assay (ELISA) or fluorescent assay (FA)


A case that is laboratory confirmed

Related Case Definition(s)