Australia is confronting its most severe diphtheria outbreak in more than three decades, and health authorities have now confirmed the nation’s first fatality from the vaccine-preventable illness since 2018. The unprecedented spread of the disease, which is concentrated largely in remote Indigenous communities across the country’s north and west, has triggered a national public health response aimed at ramping up vaccination coverage and containing transmission.
The outbreak first began to emerge in late 2025, with case counts climbing steadily through the start of 2026 before surging sharply in February. By March, Northern Territory (NT) officials formally declared a public health outbreak, with additional cases soon detected in Western Australia (WA), South Australia, and Queensland. As of mid-2026, total confirmed cases across the country have reached 245 – making this the largest national outbreak recorded since 1991.
On Tuesday, NT Health Minister Steve Edgington announced that autopsy analysis conducted by an overseas laboratory confirmed diphtheria as the cause of a man’s death in April at Royal Darwin Hospital. This marks the first recorded diphtheria death in Australia in eight years, per national public health records.
Breaking down the geographic distribution of cases, 60% of all 2026 infections have been recorded in the Northern Territory, with Western Australia accounting for another 36% of cases. Just a small handful of additional infections have been confirmed in South Australia and Queensland. Between January 2025 and May 2026, the NT alone documented 163 cases: 48 of the more dangerous respiratory diphtheria strain, and 115 cases of cutaneous diphtheria, which spreads through direct contact with infected skin lesions.
Notably, WA’s confirmation of two respiratory diphtheria cases in March marked the first time the state has recorded such cases in more than 50 years, underscoring the unusual scope of the current outbreak.
Diphtheria presents in two distinct forms, both of which are fully vaccine-preventable. Respiratory diphtheria, the deadlier strain, initially causes symptoms including fever, chills, and sore throat, and can progress to life-threatening breathing and swallowing complications. Cutaneous diphtheria, by contrast, typically causes slow-healing sores or ulcers on exposed skin and rarely results in severe illness.
Australia’s standard national immunization schedule includes five doses of diphtheria vaccine for children between the ages of two months and four years, followed by a booster shot for adolescents between 12 and 13 years. Public health authorities are now urgently urging people in affected communities to ensure their vaccinations are up to date, particularly teenagers and adults who may be due for a booster dose.
In recent weeks, Australian officials have scaled up emergency vaccination efforts in high-risk regions, and data as of Tuesday shows new case numbers have begun to decline. Since March 30, more than 10,400 vaccine doses have been administered in the NT alone, with pop-up vaccination clinics set up in Darwin, Katherine, and Alice Springs to expand access and raise public awareness of the outbreak.
“Our government has taken this situation very seriously, and we are working hard to understand the causes and working to contain the situation,” Edgington said in Tuesday’s announcement. NT Health officials emphasized that vaccination remains “the most important measure for preventing, protecting and reducing transmission” of the disease.
Last week, national Chief Medical Officer Professor Michael Kidd formally designated the diphtheria outbreak a communicable disease incident of national significance, triggering a coordinated federal response. The federal government has also committed AU$7.2 million in emergency funding to expand vaccination capacity and boost public health resources in affected communities across the country.