Clinician Alert – Diphtheria

Health alert

Status:
Active
Alert number:
20260422
Date issued:
22 Apr 2026
Issued by:
Dr Caroline McElnay, Chief Health Officer
Issued to:
Health Professionals

Key messages

  • There is a current outbreak of diphtheria in northern and central Australia, predominantly among Aboriginal and Torres Strait Islander people.
  • No cases have been identified in Victoria to date.
  • Health care professionals should consider diphtheria in patients with compatible respiratory or cutaneous illness, particularly those with recent travel to, or contact with people from, affected Aboriginal and Torres Strait Islander communities.
  • Suspected or confirmed cases must be notified immediately by phone to Local Public Health Units by calling 1300 651 160.
  • Check if Aboriginal and Torres Strait Islander patients and other groups at risk are up‑to‑date with diphtheria vaccination and offer vaccination in line with the Australian Immunisation Handbook.

What is the issue?

To 14 April 2026, 84 diphtheria cases have been notified nationally (55 in Northern Territory; 26 in Western Australia; 2 in Queensland and 1 in South Australia).

The number of diphtheria cases reported in Australia in 2026 to date substantially exceeds the total annual number of cases recorded in any previous year since national surveillance began.

91% of cases have been among Aboriginal and Torres Strait Islander people.

Most cases (77%) have been cutaneous infections, 18% were respiratory infections. 4% were unclassified.

Who is at risk?

  • Aboriginal and Torres Strait Islander people, particularly those living in or with links to remote communities affected by the current outbreak.
  • People who are not fully vaccinated against diphtheria or are overdue for boosters.

Symptoms and transmission

Diphtheria is an acute bacterial infection caused by toxigenic strains of Corynebacterium diphtheriae (C. diphtheriae).

Cutaneous diphtheria typically presents as a shallow skin ulcer with a grey membrane.

Respiratory diphtheria commonly presents with sore throat, low‑grade fever and cervical lymphadenopathy, followed by development of a white exudate and adherent grey pseudomembrane, which can lead to airway obstruction.

Diphtheria is transmitted through respiratory droplets, direct contact with cutaneous lesions and less commonly via fomites. The incubation period is usually 2–5 days but may be longer (range 1-10 days).

Recommendations for health professionals

Testing

  • For suspected respiratory diphtheria: collect a throat swab for culture for diphtheria.
  • For suspected cutaneous disease: collect a swab of the lesion and the throat.
  • A bacterial swab should be used (not with viral transport medium). Swab beneath part of the pseudomembrane if one is present.
  • Selective medium is required to culture C. diphtheriae, therefore your pathology service should be notified that diphtheria is clinically suspected. All isolates should be sent to Microbiological Diagnostic Unit Public Health Laboratory for C. diphtheriae toxin gene detection by polymerase chain reaction (PCR).

Treatment

  • If diphtheria is confirmed or strongly suspected, consult an infectious diseases physician regarding antibiotic therapy and the need for diphtheria antitoxin.

Notification

  • Notify any suspected cases to your Local Public Health Unit immediately by calling 1300 651 160.

Vaccination

  • Diphtheria-toxoid containing vaccines (dTpa, DTPa and dT vaccines) protect against severe toxin-mediated disease.
  • Vaccinated people can still carry toxigenic bacteria in their nose and throat and transmit it to other people.
  • Ensure Aboriginal and Torres Strait Islander patients and other at‑risk groups are up‑to‑date with diphtheria vaccination in line with the Australian Immunisation Handbook .
  • Travellers to an outbreak setting, including within Australia, may consider a booster dose if more than 5 years have passed since their last diphtheria-containing vaccine.

Updated

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