Criteria

Centers for Disease Control and Prevention (CDC): anthrax (Bacillus anthracis) 2018 case definition[2]

Clinical criteria

  • An illness with at least one specific or two non-specific symptoms and signs that are compatible with cutaneous, ingestion (gastrointestinal/oropharyngeal), inhalation, or injection anthrax; systemic involvement; or anthrax meningitis; or

  • A death of unknown cause and organ involvement consistent with anthrax.

Laboratory criteria

  • Presumptive laboratory criteria for B anthracis or B cereus expressing anthrax toxins:

    • Gram stain demonstrating gram-positive rods, square-ended, in pairs or short chains

    • Positive result on a test with established performance in a Clinical Laboratory Improvement Amendments (CLIA)-accredited laboratory.

  • Confirmatory laboratory criteria for B anthracis or B cereus expressing anthrax toxins:

    • Culture and identification from clinical specimens by Laboratory Response Network (LRN)

    • Demonstration of B anthracis antigens in tissues by immunohistochemical staining using both B anthracis cell wall and capsule monoclonal antibodies;

    • Evidence of a four-fold rise in antibodies to protective antigen between acute and convalescent sera or a four-fold change in antibodies to protective antigen in paired convalescent sera using CDC quantitative anti-PA immunoglobulin G (IgG) enzyme-linked immunosorbent assay (ELISA) testing in an unvaccinated person

    • Detection of B anthracis or anthrax toxin genes by the LRN-validated PCR and/or sequencing in clinical specimens collected from a normally sterile site (such as blood or cerebrospinal fluid) or lesion of other affected tissue (skin, pulmonary, reticuloendothelial, or gastrointestinal);

    • Detection of lethal factor (LF) in clinical serum specimens by LF mass spectrometry.

Case classification

  • Suspected: a case that meets the clinical criteria and for whom an anthrax test was ordered, but with no epidemiological evidence relating it to anthrax.

  • Probable: a case that meets the clinical criteria and has presumptive laboratory test results; or a case that meets the clinical criteria and has epidemiological evidence relating it to anthrax.

  • Confirmed: a case that meets the clinical criteria and has confirmatory laboratory test results.

The full case definition should be consulted for a clinical description of the four types of anthrax (as well as anthrax meningitis) and a definition of epidemiological linkage.[2]

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