Australia struggles to contain worst diphtheria outbreak in decades after over 220 cases reported

Australia is grappling with its “biggest diphtheria outbreak“ in decades as the bacterial infection continues to spread through Northern Territory.

The country’s top medical body is now urging all Australians to ensure they are fully vaccinated against diphtheria following a resurgence of the Victorian-era disease.

Most of the nearly 220 cases reported so far are in Northern Territory, Western Australia, South Australia, and Queensland.

Diphtheria can cause swollen glands, breathing problems and fever. The bacterial disease mostly affects children.

It was considered almost eradicated following a vaccination rollout that began in the 1930s.

The current outbreak is being blamed on a dip in vaccination rates. Cases began to rise in 2025, prompting the Northern Territory Centre for Disease Control to declare an outbreak in March.

Almost all cases have involved Indigenous Australians, which has pushed health authorities to work with Aboriginal agencies to improve immunisation.

Health authorities were awaiting the outcome of an investigation into a suspected diphtheria death, which could be the first fatality from the disease in almost a decade.

"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,” federal health minister Mark Butler said.

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Source: The Independent, 20 May 2026