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Plague (Yersinia pestis)
1990 Case Definition

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