Case Definition
Confirmed Case
Clinical illness and laboratory confirmation of infection: isolation of Yersinia pestis from body fluids
OR - a significant (e.g. fourfold or greater) rise in serum antibody titre to Y. pestis fraction 1 (F1) antigen by EIA or passive hemagglutination / inhibition titre
OR - positive for specific bacteriophage lysis AND demonstration of Y. pestis F1 antigen by immunofluorescence
OR - positive for specific bacteriophage lysis AND detection of Y. pestis nucleic acid
OR - >1/10 passive hemagglutination / inhibition titre in a single serum sample in a patient with no history of vaccination or previous infection AND demonstration of Y. pestis F1 antigen by immunofluorescence
OR - detection of Y. pestis antibody by EIA AND demonstration of Y. pestis F1 antigen by immunofluorescence
OR - >1/10 passive hemagglutination / inhibition titre in a single serum sample in a patient with no history of vaccination or previous infection AND positive for specific bacteriophage lysis
OR - detection of Y. pestis antibody by EIA AND positive for specific bacteriophage lysis
Probable Case
Clinical illness with one of the following laboratory confirmations of infection: demonstration of elevated serum antibody titre(s) to Y. pestis F1 antigen (without documented 4-significant [e.g. fourfold or greater] change) in a patient with no history of plague immunization
OR - demonstration of Y. pestis F1 antigen by immunofluorescence
OR - detection of Y. pestis nucleic acid
OR - >1/10 passive hemagglutination / inhibition titre in a single serum sample in a patient with no history of vaccination or previous infection
OR - detection of Y. pestis antibody by EIA
OR - positive for specific bacteriophage lysis
Definition of clinical illness
Clinical illness: the disease is characterized by fever, chills, headache, malaise, prostration, and leukocytosis that is manifest 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)
