Australia is currently in the midst of the largest outbreak of diphtheria in recent memory with more than 220 cases recorded.

The disease was previously considered almost eradicated but cases have popped up across the country - mainly in the Northern Territory but also in Western Australia, South Australia and Queensland.

Authorities are currently investigating a death in the NT believed to be related to diphtheria. If confirmed, it would be the first diphtheria death in almost 10 years.

Health Minister Mark Butler told a press conference on the NSW Central Coast the data was '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. 

Butler announced the federal government would work to bolster vaccination rates, which fell to their lowest 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,' he said.

'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 [it is] also starting to place pressure on hospital systems in the NT as well.'

However, experts have called for the vaccine rollout to focus on areas where access to healthcare is limited.

Adelaide University professor Adrian Esterman told the ABC many of the communities currently experiencing outbreaks are in very remote locations. 

'It's just that many of them live so far away from a health centre that they don't get the treatment and boosters they need,' Dr Esterman said.

But the drop in vaccine rates recorded since 2020 isn't just limited to rural areas, but also part of the wider anti-vaccine movement - largely caused by online misinformation spread during the Covid vaccine rollout. 

'When you look at the timeline of this epidemic, you can see it start to rise after 2020 [and] after 2025 it has really gone up,' biosecurity professor at the Kirby Institute, Raina MacIntyre, said.

'The remoteness and the healthcare access hasn't changed. That's not the factor that's changed that can explain this epidemic.

'The factor that has changed is the falling vaccination rates.'

The Central Australian Aboriginal Congress health service's John Boffa also spoke to the ABC, said the NT was also grappling with a 'depleted workforce'.

'We've had a very severe workforce crisis post Covid, and we're not out of that yet. There's actually no signs yet that we're going to see major improvements,' he said.

'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.'

Diphtheria is a highly contagious, and potentially, fatal bacterial infection that attacks the nose and throat.

Symptoms include a grey membrane over the throat and tonsils, a sore throat, swollen lymph nodes, difficulty breathing, nasal discharge, fever, chills and tiredness.

Those who suspect they have diphtheria are advised to call Health Direct on 1800 022 222.