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Case definition

Confirmed case

Clinical illness or systemic manifestations compatible with diphtheria in a person with an upper respiratory tract infection or infection at another site (such as a skin wound) plus at least one of the following: 

  • Laboratory confirmation of infection: 
    • Isolation of Corynebacterium diphtheriae with confirmation of toxin from an appropriate clinical specimen including the exudative membrane OR 
    • Isolation of other toxigenic corynebacteria species (Corynebacterium ulcerans or Corynebacterium pseudotuberculosis) from an appropriate clinical specimen, including the exudative membrane OR
    • Histopathologic diagnosis of diphtheria
  • Epidemiologic link (contact within 2 weeks prior to onset of symptoms) to a laboratory-confirmed case

Probable case

Clinical illness in the absence of laboratory confirmation or epidemiological link to a laboratory-confirmed case. 

Diphtheria carrier

A carrier is defined as a person who harbours and may disseminate toxigenic C. diphtheriae (or C. ulcerans or C. pseudotuberculosis) but who manifests no upper respiratory tract (pharyngitis or laryngitis) or systemic symptoms. Carriers include those with otitis media, nasal or cutaneous infections and asymptomatic pharyngeal infections due to toxigenic C. diphtheriae (or C. ulcerans or C. pseudotuberculosis).

Definition of clinical illness 

Clinical illness is characterized as an upper respiratory tract infection (nasopharyngitis, laryngitis, or tonsillitis) with or without an adherent nasal, tonsillar, pharyngeal or laryngeal membrane, plus at least one of the following: 

  • Gradually increasing stridor (harsh, vibrating breath sound)
  • Cardiac (myocarditis) or neurologic involvement (motor or sensory palsies) 1 to 6 weeks after onset 
  • Death, with no known cause
SOURCE: Diphtheria ( )
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