Clinician Alert - Diphtheria

Key points:

• There is a large outbreak of diphtheria, primarily among Aboriginal and Torres Strait Islander people across northern and central Australia.
• Clinicians should consider diphtheria when a patient presents with a clinically compatible illness, especially if they have had direct or indirect contact with a remote Aboriginal community.
• Ensure all patients are up to date with diphtheria vaccinations.
• Notify your local public health unit immediately of any suspected diphtheria cases.

Situation

• From 1 January to 17 April 2026, 88 cases of diphtheria have been notified in Australia; markedly higher than in all previous years since the commencement of national notification in 1991.

• Of these:

• 86% were cutaneous infections, and 14% were respiratory infections
• 56 cases were in NT, 29 in WA, 2 in Qld and 1 in SA
• 91% of cases were among Aboriginal and Torres Strait Islander people.

Clinical presentation and treatment

• Cutaneous diphtheria

• Chronic, non-healing sores or shallow ulcers that can develop a greyish membrane

• Respiratory diphtheria

• Sore throat, low grade fever, pharyngeal exudate and a greyish white pseudomembrane overlying the tonsils, pharynx or nasal passages, enlarged anterior cervical lymph nodes and soft tissue oedema.

• For suspected respiratory diphtheria, take a throat or nasopharangeal swab for culture and PCR testing. For suspected cutaneous cases, swab the ulcer and the throat. The request form should state “URGENT – culture for suspected diphtheria” to expedite processing.

• Ensure standard and droplet precautions are used when taking swabs for testing including a surgical mask, glasses, gloves and gown. Isolate suspected cases immediately.

• Seek specialist infectious disease advice on appropriate antibiotic therapy and the need for diphtheria antitoxin (DAT). Guidance is available on how to access DAT in Queensland via the Special Access Scheme.

• Respiratory diphtheria is a medical emergency.

Vaccination

• Diphtheria is vaccine-preventable with diphtheria-toxoid vaccine; dTpa, DTPa and dT vaccines.

• Vaccination primarily protects a person from severe, toxin-mediated disease rather than preventing infection or onward transmission.

• Children are recommended to receive 5 doses of a diphtheria-toxoid vaccine at 2, 4, 6 and 18 months, and 4 years of age. Adolescents should receive a dose at 11-13 years of age.

• Children who have not received 5 doses should have catch-up vaccines and adults who did not have an adolescent dose should be vaccinated.

• A diphtheria-toxoid vaccine booster is recommended for adults at 50 years of age and again at 65 years of age, if they have not had a dose in the previous 10 years.

• It is recommended that healthcare providers proactively check the vaccination history for all patients and administer appropriate vaccinations for those who are not up-to-date.

Further information

Australian Immunisation Handbook | Diphtheria

Fact sheet Diphtheria | Queensland Health

Dr Heidi Carroll, Executive Director, Communicable Diseases Branch, Queensland Health

17 April 2026

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