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: 28 June 2013



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.

Probable case

A probable case requires:

Laboratory suggestive evidence AND clinical evidence


Clinical evidence AND epidemiological evidence.

Laboratory suggestive evidence

Isolation of Corynebacterium diphtheriae or C. ulcerans(toxin production unknown).

Clinical evidence

At least one of the following:

Pharyngitis and/or laryngitis (with or without a membrane)


Toxic (cardiac or neurological) symptoms.

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.

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