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Plague (Yersinia pestis)
1996 Case Definition

CSTE Position Statement(s)

  • 09-ID-52

Clinical Description

Plague is transmitted to humans by fleas or by direct exposure to infected tissues or respiratory droplets; the disease is characterized by fever, chills, headache, malaise, prostration, and leukocytosis that manifests 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 pneumonic plague) or inhalation of infectious droplets (primary pneumonic plague)
  • Pharyngitis and cervical lymphadenitis resulting from exposure to larger infectious droplets or ingestion of infected tissues (pharyngeal plague)

Laboratory Criteria for Diagnosis


  • Elevated serum antibody titer(s) to Yersinia pestis fraction 1 (F1) antigen (without documented fourfold or greater change) in a patient with no history of plague vaccination, OR
  • Detection of F1 antigen in a clinical specimen by fluorescent assay
  • Isolation of Y. pestis from a clinical specimen, OR
  • Fourfold or greater change in serum antibody titer to Y. pestis F1 antigen

Case Classification


A clinically compatible case without presumptive or confirmatory laboratory results


A clinically compatible case with presumptive laboratory results


A clinically compatible case with confirmatory laboratory results


The 1996 case definition appearing on this page was re-published in the 2009 CSTE position statement 09-ID-52. Thus, the 1996 and 2010 versions of the case definition are identical.