Diphtheria case definition

This document contains the case definitions for Diphtheria which is nationally notifiable within Australia. This definition should be used to determine whether a case should be notified.

Page last updated: 17 January 2017


Both confirmed cases and probable cases should be notified.

Confirmed case

A confirmed case requires laboratory definitive evidence and clinical evidence.

Laboratory definitive evidence

Isolation of toxigenic* Corynebacterium diphtheriae or toxigenic* C. ulcerans from site of clinical evidence.

Clinical evidence – confirmed case

  • Upper respiratory tract infection


  • Skin lesion

Probable case

A probable case requires:

  • Laboratory suggestive evidence and clinical evidence


  • Clinical evidence and epidemiological evidence.

Laboratory suggestive evidence

Isolation of C. diphtheriae or C. ulcerans from a respiratory tract specimen (toxin production unknown).

Clinical evidence - probable case

Upper respiratory tract infection with an adherent membrane of the nose, pharynx, tonsils or larynx

Epidemiological evidence

An epidemiological link is established when there is:

Contact between two people involving a plausible mode of transmission at a time when:

  1. one of them is likely to be infectious (usually 2 weeks or less and seldom more than 4 weeks after onset of symptoms)


  1. the other has an illness which starts within approximately 2-5 days after this contact


At least one case in the chain of epidemiologically linked cases (which may involve many cases) is laboratory confirmed.

*as indicated by detection of toxin gene by nucleic acid testing

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