Diphtheria outbreak in Australia: low current risk for Aotearoa New Zealand

An ongoing diphtheria outbreak across several Australian states and territories is being closely monitored, with the current risk of introduction to New Zealand considered low.

The Northern Territory (NT) is experiencing a significant outbreak that has spread to parts of Western Australia, Queensland, and South Australia. As at 27 April 2026, 117 cases have been reported this year — the majority among Indigenous peoples (92%) and in rural and remote areas (98%). Around a quarter of cases involve respiratory diphtheria; the remainder are cutaneous (skin) disease.

While the overall risk to New Zealand remains low, the risk of an outbreak increases in areas with lower vaccination coverage if diphtheria is introduced — particularly in high-density settings.

What clinicians should look out for

Be alert for diphtheria in returning travellers from Australia and regions where diphtheria is endemic, including Asia and the South Pacific, who present with:

• severe acute respiratory illness, or
• non-healing ulcers.

Vaccination remains the key protective measure

Please continue to encourage vaccination during pregnancy and support on-time infant and childhood immunisation. Catch-up vaccinations should be offered to anyone not yet fully vaccinated.

For full risk information and key messages for healthcare professionals, please refer to the public health advisory (PDF).