Australia faces largest diphtheria outbreak in decades, with over 220 cases

Federal and state governments have mobilised to address the largest outbreak of diphtheria in recent memory, with the Commonwealth preparing a support package to bolster vaccination rates for a disease once considered almost eradicated.

There have now been more than 220 cases of diphtheria reported so far this year across Australia, primarily in the Northern Territory but also in Western Australia, South Australia and Queensland.

Authorities are also waiting on the outcome of an investigation into a reported diphtheria-related death in the NT, which would be the first death from the disease in almost a decade.

Federal health minister Mark Butler said the numbers were "very concerning."

"To put that in context, we've been recording case numbers nationally for about 35 years, and this, by a very big distance, is the biggest outbreak of diphtheria we've ever seen," he said.

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The federal government is now working on a support package primarily aimed at boosting waning vaccination rates, with routine childhood immunisation coverage — which includes the diphtheria vaccine — falling to its lowest level in five years in 2025.

"More vaccines, a surge workforce is part of the package that we'll be finalising over the course of today, working closely with the NT government and with the Aboriginal controlled sector, because this is overwhelmingly an outbreak being experienced by Indigenous Australians in the NT," Mr Butler said at a press conference on the NSW Central Coast.

"I want to say this is not just very serious in terms of its numbers, but the vast majority of new cases we're seeing are respiratory diphtheria, which is far more serious in terms of its potential — about 25 per cent of cases are being hospitalised.

"So this is obviously a deep concern for people who are exposed to this disease, but also starting to place pressure on hospital systems in the NT as well."

The Central Australian Aboriginal Congress health service's John Boffa said while health services were working hard to try to boost vaccination rates in the NT, it was "on the back of a depleted workforce".

"We've had a very severe workforce crisis post COVID, and we're not out of that yet. And there's actually no signs yet that we're going to see major improvements," he told the ABC.

"Where I work, which is a large Aboriginal health service, we're 10 full time equivalent GPs down on what we should have… we're down probably 20 nursing positions as well. And I know that the health department is really struggling as well in the remote clinics.

"There's got to be a better policy response to address mal-distribution of workforce across this country. But that's the situation we're in. So we're doing as well as we can with outreach vaccination."

What is diphtheria?

Diphtheria is a life-threatening and highly contagious bacterial infection that is treated with antibiotics.

Respiratory diphtheria can affect the nose, throat and airways, while cutaneous diphtheria can affect the skin.

It spreads through respiratory droplets from coughing or sneezing, or direct contact with infected wounds.

Even with treatment, one in 10 people with respiratory symptoms die, according to the Australian Centre for Disease Control.

Historically, diphtheria was a leading cause of childhood death globally and, according to the National Centre for Immunisation Research and Surveillance Australia, more than 4,000 Australians died from the disease between 1926 and 1935.

But vaccination started in Australia in the 1930s, and since the 1950s, the disease has been considered largely eliminated.

Peter Collignon, professor at the ANU Medical School in Infectious Diseases, said it was unclear what specifically had caused that to change.

He said while low vaccination rates were a main factor, diphtheria also disproportionately affected people in lower socio-economic areas, where poor housing and crowding made the disease easier to spread.

"I'm not sure we'll ever be able to unravel it, but it's often a combination of factors… people who may have been more infectious got together in bigger crowds with less people who were immunised. And that means there's more cases," Professor Collignon said.

"With all these diseases, prevention is much better than a cure, and prevention is basically trying to fix some of the socio-economic conditions, but also making sure you have people fully vaccinated, because essentially that gets rid of the disease."

Australian Medical Association President Dr Danielle McMullen said the steep rise in diphtheria cases highlighted the importance of vaccines.

"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," Dr McMullen said.

"We are seeing that risk play out with diphtheria, and it is a timely reminder for Australians to check they are up to date and to talk to their usual GP if they have questions."