Australia faces its largest diphtheria outbreak in decades, with more than 220 cases recorded so far in 2026 and the bacterial infection spreading across four states and territories, chiefly among Indigenous communities in remote areas.
Federal Health Minister Mark Butler said the number of notified cases this year is 29.8 times higher than the equivalent periods between 2022 and 2025. The outbreak has already surpassed any single year’s total in the past quarter-century, with the Northern Territory Centre for Disease Control having declared an outbreak in March after a sharp rise in cases that began in late 2025 and accelerated rapidly in February.
According to the National Notifiable Disease Surveillance System, 133 of the cases are in the Northern Territory, 79 in Western Australia, six in South Australia, and five in Queensland. The most severely affected regions include the Kimberley, Goldfields and Pilbara in Western Australia, the far north-west of South Australia, and the APY Lands in South Australia.
Affected communities
Nearly all cases have involved Indigenous Australians, a pattern that has forced health authorities to work closely with Aboriginal community-controlled health services to improve immunisation coverage and contain the outbreak. The majority of infections are respiratory diphtheria, which the minister described as “far more serious in terms of their potential.” About one in four cases are being hospitalised — 24.7 per cent so far in 2026 — placing considerable strain on hospital systems in the Northern Territory.
Mr. Butler said the government is finalising a support package that will include additional vaccine doses and a surge workforce, developed in partnership with the Northern Territory government and the Aboriginal-controlled sector.
Why vaccination rates have fallen — and the consequences
The resurgence of a disease that was considered almost eradicated after vaccination programs began in the 1930s has been blamed squarely on a dip in vaccination coverage. Routine childhood immunisation fell to a five-year low in 2025, and nationally, coverage at 24 months dropped below 90 per cent in 2024 for the first time since 2016.
Diphtheria was once a leading cause of childhood death globally. In Australia alone, more than 4,000 deaths were recorded between 1926 and 1935. Widespread vaccination turned it into a rarity, but the current outbreak demonstrates how fragile that achievement is. Immunisation expert Dr. Milena Dalton said the outbreak shows how quickly vaccine-preventable diseases can re-emerge because of gaps in immunisation. “Although diphtheria remains rare in Australia this outbreak shows it hasn’t disappeared,” she said.
Professor Adrian Esterman added that diphtheria “does not return to a population by chance”; it reappears where vaccination coverage has slipped and living conditions allow the disease to spread. Overcrowded housing has been identified as a contributing factor, particularly in remote Indigenous communities.
Expert warnings and clinical context
The outbreak involves both respiratory and cutaneous (skin) diphtheria. Respiratory diphtheria typically begins with a sore throat, mild fever and swollen glands, and can lead to a thick grey-white coating — called a pseudomembrane — forming at the back of the throat, nose, or on the tongue, causing difficulty breathing and swallowing. In severe cases it can cause airway obstruction and death from asphyxia. Cutaneous diphtheria presents as chronic, non-healing sores or shallow ulcers, often covered by a grey membrane. While generally less serious, it can still infect others and lead to respiratory diphtheria.
Transmission occurs through respiratory droplets from coughs and sneezes, direct contact with infected skin lesions, or sharing personal items such as cups, cutlery, clothing and bedding. Symptoms usually appear between two and five days after infection.
Dr. Ramya Raman, vice president of the Royal Australian College of General Practitioners and its Western Australia chair, urged GPs to remain vigilant for both respiratory and cutaneous presentations of the disease. Associate Professor Erin Price, a microbiology researcher, noted that the outbreak is significant because it affects First Nations communities across multiple states and territories.
A concerning development is a suspected diphtheria death in the Northern Territory, involving an adult. Health authorities are awaiting the results of an investigation. If confirmed, it would be the first fatality from diphtheria in Australia since 2018.
