National case definition: Diphtheria

Date of last revision/review: May 2008

National reporting

Only confirmed cases of disease should be notified.

Type of surveillance

Routine case-by-case notification to the federal level

Case classification

Confirmed case

Clinical illness (see Clinical Evidence section) or systemic manifestations compatible with diphtheria in a person with an upper respiratory tract infection or infection at another site (e.g. wound, cutaneous) 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 Corynebacterium species (C. ulcerans or C. pseudotuberculosis) from an appropriate clinical specimen, including the exudative membrane

  or

  • histopathologic diagnosis of diphtheria

or

• Epidemiologic link (contact within two weeks prior to onset of symptoms) to a laboratory-confirmed case

Probable case

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

Suspect case

Upper respiratory tract infection (nasopharyngitis, laryngitis or tonsillitis) with or without a nasal, tonsillar, pharyngeal and/or laryngeal membrane

Laboratory Comments

Isolation of Corynebacterium species capable of producing diphtheria toxin (C. diphtheriae, C. ulcerans or C. pseudotuberculosis) should be tested using the modified ELEK assay OR assay for the presence of the diphtheria tox gene, which, if detected, should be tested for expression of diphtheria toxin using the modified ELEK assay

Clinical evidence

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

• gradually increasing stridor
• cardiac (myocarditis) and/or neurologic involvement (motor and/or sensory palsies) one to six weeks after onset
• death, with no known cause

ICD code(s)

ICD-10 code(s)

A36 Diphtheria

ICD-9/ICD-9CM code(s)

032 Diphtheria

Comments

Suspect and probable case definitions are provided as guidelines to assist with case finding and public health management, and are not for national notification purposes.

Although rare, other toxigenic Corynebacterium species (C. ulcerans or C. pseudotuberculosis) may cause clinical diphtheria. Cases with clinically compatible illness and isolation of other toxigenic Corynebacterium species are nationally notifiable.

Significant, systemic disease is occasionally caused by non-toxigenic strains of these species in specific patient populations.

References

Laboratory Centre for Disease Control. Guidelines for the control of diphtheria in Canada. CCDR 1998;24(S3).

De Winter LM, Bernard KA, Romney MG. Human clinical isolates of Corynebacterium diphtheriae and Corynebacterium ulcerans which do not meet the criteria for notifiable diphtheria in Canada 1999-2003. J Clin Microbiol 2005;43:3447-9.

Romney MG, Roscoe DL, Bernard K, Lai S, Efstratiou A, Clarke AM. Emergence of an invasive clone of non-toxigenic Corynebacterium diphtheriae in Vancouver's urban poor. J Clin Microbiol 2006;44:1625-9.

Previous case definitions

Canadian Communicable Disease Surveillance System: disease-specific case definitions and surveillance methods. Can Dis Wkly Rep 1991;17(S3).

Case definitions for diseases under national surveillance. CCDR 2000;26(S3)