Measles and diphtheria outbreaks rise in Australia amid declining vaccination rates

Contracting a case of measles and enduring the fever, cough, sore eyes and characteristic red rash was a common part of growing up before vaccination was introduced.

The disease was so rampant in Australia that anyone born before the late 1960s is thought to be immune, as it's likely they've already had the disease as a child.

Since then, Australia has eliminated the highly-contagious virus through a vaccination campaign and has held the status of an endemic measles-free country for more than a decade.

A recent outbreak in South Australia spreading within a school community has sparked concern from health authorities, but it's not the only uncommon disease that has recently spiked in cases.

Australia is also experiencing the largest diphtheria outbreak since records began, with the cases predominantly among Indigenous people in outer regional and remote areas across four states and territories.

So what's happening and why?

Where are measles cases coming from?

The World Health Organisation declared Australia free of endemic measles in 2014, meaning there is no ongoing local transmission within the population, although cases can still be brought in from overseas.

South Australia's latest outbreak was sparked by the return of a traveller who contracted the disease overseas and had since spread it to three other students and an adult in their 40s, who was hospitalised, within the Brighton Secondary School community.

Contract tracing is being undertaken after the adult spent more than 24 hours at the Queen Elizabeth Hospital's emergency department.

The outbreak takes SA's measles total so far this year to nine, the highest since 2016.

According to SA's Chief Public Health Officer Nicola Spurrier, it was a "disappointing" development but not altogether surprising given anti-vaccination misinformation.

"I have seen our vaccination rates year on year since the [COVID-19] pandemic starting to drop … I see what information is being provided in other forms other than the science," Professor Spurrier told the ABC.

Why is measles coming back?

Adelaide University professor and epidemiologist Adrian Esterman said measles vaccine access was also a contributing factor to the sliding rates.

"It's things like parents being very busy, trouble getting to see the GP, I think it's more things like that rather than people hesitating to get their children vaccinated," Professor Esterman said.

He said cases of measles have also been surging overseas.

"Canada has now lost its measles-free status, the UK has lost its measles-free status, the USA is almost certainly going to be losing it shortly," he said.

Professor Esterman said measles, diphtheria and even whooping cough, which saw a national spike in cases in 2024, are all examples of childhood diseases which are making a comeback due to declining childhood vaccinations.

"All of these various childhood diseases, they used to be absolute killers 80-100 years ago," he said.

"Most families had large numbers of children because they knew so many would actually die during the first year."

What's happening with the diphtheria outbreak?

The latest surge of diphtheria infections — the largest outbreak in Australia since records began in 1991 — has now risen to more than 600 cases, 22 of which were in SA.

The highly contagious bacterial infection, which affect the nose, throat, airways or the skin, is treated with antibiotics and vaccination is considered the primary line of defence against the disease.

SA Health said cases have been plateauing in recent weeks as more than 4,500 vaccines have been delivered to communities in the far north and south-west.

"Up in the APY Lands where we've had the majority of the cases, there has been really high vaccinations so we're extremely pleased with the community's response," Professor Spurrier said.