Experts are calling for increased vaccination efforts as case numbers reach unprecedented heights.
Australia is experiencing its worst outbreak of diphtheria since the infection became a nationally notifiable condition, with the Indigenous population being hit hardest.
The National Notifiable Disease Surveillance System has received over 220 notifications of diphtheria between 1 January and 20 May – more than any full calendar year since national reporting began. The Northern Territory (133) and Western Australia (82) have borne the brunt of the outbreak to date, with South Australia (6) and Queensland (< 5) also recording cases this year.
Fewer than 40 cases were reported in 2025, and between 2011 and 2025 there was only one instance of a state or territory reporting double-digit cases of diphtheria – Queensland in 2022 (25).
Earlier today, the ABC reported that the federal government was preparing a support package designed to increase vaccination rates for a range of infectious disease, including diphtheria, consisting of additional vaccine doses and a surge workforce.
The exact details of the package were not confirmed at time of writing but are expected soon.
“Australia is currently in the midst of our worst diphtheria outbreak in decades. This outbreak is significant because it’s affecting a broad swathe of First Nations communities across multiple Australian states and territories, with high case numbers and one likely death to date,” said Associate Professor Erin Price, a microbiology researcher from the University of the Sunshine Coast.
The current outbreak has been catalysed by falling vaccination rates, according to Professor Adrian Esterman, chair of biostatistics at Adelaide University.
“Diphtheria does not return to a population by chance. It returns where vaccination coverage has slipped and where living conditions allow it to spread,” he said in a statement.
“Nationally, childhood vaccination coverage at 24 months fell below 90% in 2024 for the first time since 2016. That weakens community protection across Australia.”
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Speaking on ABC Radio National yesterday, federal health minister Mark Butler said the government was “very concerned” about the situation, especially regarding reports of a potential diphtheria-related death.
“This is probably the biggest diphtheria outbreak we’ve seen, certainly for decades. I was up Alice Springs a couple of weeks ago meeting with the Aboriginal Medical Service for the Northern Territory. They’re obviously deeply, deeply concerned. Almost all of the cases are Indigenous Australians.
“There has been a report of a death, although the NT Government is still investigating that. We’re waiting to see the advice of that investigation, but there’s no question this is serious. It’s serious in the NT. It’s spreading across other parts of the Top End. It’s crept below the South Australian border into the APY Lands. So we’re working very closely with the NT Government, but also with the Aboriginal-controlled sector.”
The Australian Medical Association has urged Australians to check their vaccinations are up to date as diphtheria numbers rise across the state.
“Immunisation is one of the greatest achievements in modern medicine, but when vaccination rates fall, serious diseases, which we had largely eliminated, can make a comeback,” said AMA president Dr Danielle McMullen.
“We are seeing that risk play out with diphtheria, and it is a timely reminder for Australians to check they are up to date with their vaccines and to talk to their usual GP if they have questions.”
Jaya Dantas, a professor of international health from the School of Population Health at Curtin University, said federal and state health departments needed to make “a concerted effort” to address the outbreak.
“For over 50 years Australia had no cases of diphtheria, so this resurgence highlights a reduction in vaccination rates and boosters. We need all of the population in the Northern Territory and Central Australia and WA in the impacted communities to be vaccinated or receive a booster with urgency. We need to expand vaccinations under the National Immunisation Program where childhood vaccination is completely free under the scheme, but with the adults, it’s still not the case,” they told media.
Diphtheria is caused by certain strains of the Corynebacterium diphtheriae bacterium.
“These highly contagious microorganisms infect the skin and upper respiratory tract, and can produce diphtheria toxin. Early symptoms include a mild fever, sore throat and swollen neck glands, or skin sores with local swelling and tissue damage in cutaneous cases. Symptoms can worsen as the bacterium blocks the airways, and the toxin can spread via blood, causing heart failure and paralysis,” Professor Price said.
Further information on diphtheria and the available vaccines can be found on the Australian Centre for Disease Control website. Information about which diphtheria vaccines are covered under the National Immunisation Program is available on the Department of Health, Disability and Ageing website.
