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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.

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.

Related Case Definition(s)