A significant diphtheria outbreak, the largest since national record-keeping began in 1991, has spread across multiple Australian states and territories as of mid-2026. The outbreak is primarily concentrated in remote Aboriginal communities, with health authorities reporting over 260 cases and one confirmed death. The federal government has announced a AUD $7.2 million support package to bolster vaccination efforts and public health response.
Outbreak Overview and Timeline
The Australian Centre for Disease Control (CDC) reported that diphtheria notifications have been increasing since October 2025, with a marked surge beginning in February 2026. The number of cases in 2026 is approximately 30 times the average for the equivalent period between 2022 and 2025.
Key milestones in the outbreak include:
- May 2024: The first cutaneous (skin) diphtheria cases emerged in the Northern Territory.
- December 2025: An outbreak began in Western Australia's Kimberley region.
- March 2026: NT Health declared a diphtheria outbreak, the first in the territory since the 1990s.
- Late May 2026: The outbreak was declared a Communicable Disease Incident of National Significance.
- Late May 2026: The federal government announced a $7.2 million support package.
Case Numbers and Geographic Distribution
As of late May 2026, the Australian CDC reported over 260 total cases nationwide. The breakdown by jurisdiction, based on multiple official reports, is as follows:
- Northern Territory: 163 cases (115 cutaneous, 48 respiratory). An earlier internal report documented 17 respiratory cases since March 23 and 60 cutaneous cases since May 2025.
- Western Australia: 98 cases, with 55 in the Kimberley region, 3 in the Pilbara, and 2 in the Goldfields. Cases were predominantly among Aboriginal children and young adults.
- South Australia: 7 cases.
- Queensland: 3 to 5 cases.
- Other states: A targeted diphtheria booster vaccination program was announced in Victoria for travelers to high-risk areas and Aboriginal and Torres Strait Islander people, though no cases were reported there.
Note: Case numbers varied slightly across reports due to ongoing surveillance and data reconciliation.
Clinical Presentation and Demographics
The outbreak includes two main forms of the disease:
- Cutaneous Diphtheria: Accounts for approximately 70% of cases. It presents as chronic, slow-healing sores or shallow ulcers, often on the legs.
- Respiratory Diphtheria: Accounts for approximately 30% of cases. Symptoms include a sore throat, mild fever, and a grey pseudomembrane in the throat. If untreated, it can lead to difficulty breathing and life-threatening complications.
Demographics:
- 94% to 98% of cases have been among Aboriginal and/or Torres Strait Islander people.
- The majority of locally acquired cases reside in areas classified as 'remote' or 'very remote' (81.8%) or 'outer regional' (15.1%).
- 25% of all cases have required hospitalization.
- 93% of cases in the Northern Territory were among Aboriginal and Torres Strait Islander people, with cases detected across all five NT regions.
Fatalities
One death has been confirmed as diphtheria-related—an adult in the Northern Territory. This is the first diphtheria death in Australia since 2018. A second death in Central Australia was investigated but was confirmed not to be related to diphtheria.
Government Response and Federal Funding
On May 28, 2026, the federal government announced a AUD $7.2 million package to address the outbreak, following a request for assistance from the Northern Territory government.
Funding Allocation:
- $5.2 million to the National Critical Care and Trauma Response Centre (NCCTRC) to deploy a surge workforce for administering and procuring vaccines and antibiotics.
- $2 million to the National Aboriginal Community Controlled Health Organisation (NACCHO) for culturally safe communications, community liaison, and other public health supports.
Federal Health Minister Mark Butler described the outbreak as "very concerning" and the largest in decades. The funding is primarily for the Northern Territory, with the minister stating he would write to other affected states to assess their need for Commonwealth support.
Vaccination Campaign and Coverage
A mass vaccination campaign has been initiated. Over 10,000 vaccine doses were administered in the Northern Territory within seven weeks. The campaign is a partnership with Aboriginal community-controlled health services and other local healthcare providers.
Vaccination Recommendations:
- Children: Routine vaccination under the National Immunisation Program (NIP) at 6 weeks, 2 months, 4 months, 6 months, 18 months, 4 years, and 12 years.
- Adults: A booster dose every 10 years is recommended.
- At-Risk Groups: For Aboriginal and Torres Strait Islander people and healthcare workers in affected areas, a booster is recommended every 5 years.
- Pregnant Women: A booster is recommended between 20 and 32 weeks of pregnancy.
Vaccination Coverage Declines:
- National childhood immunization coverage for 5-year-olds fell to 93.4% in 2025, the lowest level in five years.
- In the Northern Territory, 91.9% of five-year-olds were fully vaccinated, the lowest rate among states and territories.
- In Western Australia, 92.2% of five-year-olds are vaccinated.
- Health officials and experts have cited a decline in routine vaccinations since the COVID-19 pandemic and waning immunity in adults without boosters as contributing factors.
Expert Commentary on Contributing Factors
Multiple experts and officials have provided perspectives on the outbreak. The following factors have been cited as potential contributors:
- Vaccination Gaps: Declining childhood vaccination rates and low adult booster uptake. The Australian Medical Association (AMA) President Dr. Danielle McMullen stated that falling vaccination rates allow serious diseases to return.
- Structural and Environmental Factors: Overcrowded housing in remote communities, limited access to healthcare services, and poor living conditions were frequently cited. Professor Adrian Esterman (University of Adelaide) noted that the outbreak is linked to lapses in vaccination coverage and poor living conditions.
- Misinformation and Vaccine Hesitancy: Professor Raina MacIntyre (Kirby Institute) attributed falling vaccination rates to misinformation and noted that vaccine hesitancy has increased since the COVID-19 pandemic.
- Waning Immunity: The Australian CDC stated that unvaccinated individuals or those whose last dose was over 10 years ago are at greater risk of severe illness.
- Outbreak Origin: NT Chief Health Officer Paul Burgess stated that genomic fingerprinting links the outbreak to previous outbreaks in North Queensland (2022-2024) and the Kimberley (2025).
Criticism of Outbreak Response
Some health workers and community organizations have criticized the pace of the official response.
- Delayed Public Alert: An internal NT Health document showed multiple cases were recorded weekly from the last week of February 2026, but a public health alert was not issued until March 25.
- Communication Gaps: Residents in the remote community of Yuendumu reported a lack of public health information about the disease. Service providers stated that no official information was provided in local Aboriginal languages until early May.
- Testing Delays: Reports from Yuendumu indicated a three-week wait for diphtheria test results, contributing to challenges in contact tracing and isolation.
- Workforce Shortages: Health officials in Western Australia noted a shortage of staff to administer vaccinations in remote areas, which is the size of Austria with 40 communities.
- Funding Allocation: Dr. John Boffa (Central Australian Aboriginal Congress) and others noted that while the federal funding package was welcome, it primarily focused on vaccination and did not include additional funds for testing, healthcare system strengthening, or housing.
Disease Background
Diphtheria is a vaccine-preventable disease caused by toxic strains of the bacterium Corynebacterium diphtheriae. The bacteria produce a toxin that can damage the heart, nerves, and kidneys.
Transmission: The disease spreads person-to-person primarily through respiratory droplets from coughs or sneezes, or via direct contact with skin lesions from infected individuals.
Symptoms:
- Respiratory Diphtheria: Sore throat, fever, loss of appetite, swollen neck glands, and a thick grey pseudomembrane that can obstruct the airway.
- Cutaneous Diphtheria: Chronic, non-healing skin sores or ulcers, often with a grey membrane.
Treatment: Both forms require prompt antibiotic treatment (penicillin or erythromycin). Severe respiratory diphtheria may also require diphtheria antitoxin, which is in limited global supply. The Australian CDC states that even with treatment, up to 10% of people with respiratory diphtheria may die.
Historical Context: Before widespread vaccination began in Australia in the 1930s and 1940s, diphtheria was a leading cause of childhood death, with over 4,000 Australians dying from the disease between 1926 and 1935. The disease became rare after the 1950s. The last fatal case in Australia before this outbreak was in 2018.
Other Infectious Disease Events
During this period, Victorian health authorities activated their Ebola response plan for the first time after a man who had recently traveled near Uganda and the Democratic Republic of Congo (DRC) presented with Ebola-like symptoms at a Melbourne hospital. Testing later confirmed the patient was not infected, and he was discharged.