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Diphtheria Cases Reported in Multiple Australian Jurisdictions

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Diphtheria Outbreak Reported Across Multiple Australian States

Health authorities in Western Australia and the Northern Territory are responding to confirmed cases of diphtheria, a bacterial infection that had become rare in Australia. Cases have also been reported in Queensland and South Australia this year.

This is an unusual event, with no similar outbreak in the territory in 26 years. – Dr. Paul Burgess, NT Chief Health Officer.

Outbreak Status by Region

Western Australia – Kimberley Region

  • The number of confirmed cases in the Kimberley region increased from 7 to 27 over a one-month period, with most cases concentrated in this area.
  • By April 2026, more than 30 confirmed cases were recorded across Western Australia.
  • Health authorities report that approximately 75% of the Kimberley cases are cutaneous (skin) infections, while 25% are respiratory infections.
  • One life-threatening respiratory case required transfer to Perth for intensive treatment.
  • The WA Country Health Service is treating the situation as an urgent public health issue. Prior to this, diphtheria had not been detected in the Kimberley for approximately 50 years.

Northern Territory

  • The Northern Territory Department of Health has declared an outbreak after confirming four recent cases of respiratory diphtheria: three in Darwin and one in Alice Springs.
  • Additionally, 33 cases of cutaneous diphtheria have been reported since 2025. Over the past year, 60 cutaneous cases have been recorded, alongside 17 respiratory cases in the past month.

Other States

  • Two cases have been reported in Queensland and one in South Australia this year.
  • A 2022 case in New South Wales was the first respiratory diphtheria case in Australia since 1992.

About Diphtheria

Diphtheria is an infectious disease caused by the bacterium Corynebacterium diphtheriae. Toxic strains of the bacteria produce a toxin that can cause severe illness.

  • Transmission: The disease spreads through respiratory droplets or contact with fluid from infected skin sores.
  • Types and Symptoms:
    • Respiratory Diphtheria: Symptoms can include sore throat, fever, loss of appetite, and swollen neck glands. A thick, gray, or white coating (a pseudomembrane) may form in the throat, potentially causing difficulty breathing. The toxin can damage the heart and nervous system.
    • Cutaneous (Skin) Diphtheria: This form typically presents as painful, slow-healing sores or ulcers, often with a gray covering.
  • Severity and Treatment: Respiratory diphtheria can be life-threatening if untreated. According to the Australian Centre for Disease Control, even with antibiotic treatment, up to 10% of people with respiratory symptoms may die, with a higher mortality rate among children. Treatment involves antibiotics; respiratory cases may also require a diphtheria antitoxin, which is in limited global supply. Cutaneous diphtheria is generally less severe but can transmit the bacteria.

Public Health Response

Health authorities have implemented several control measures:

  • Contact tracing systems have been established for identified cases.
  • Targeted diphtheria vaccine booster programs have been implemented in affected communities.
  • Clinicians in several regions, including the Kimberley, Pilbara, and Goldfields, are advised to watch for patients with suspicious skin sores or respiratory illness.
  • At-risk individuals are being supported to receive booster vaccinations.
  • The Northern Territory Centre for Disease Control has issued a public health alert.

Vaccination Information

Diphtheria is preventable by vaccination. The DTPa/dTpa vaccine, which protects against diphtheria, tetanus, and pertussis (whooping cough), is part of Australia's routine childhood immunization schedule under the National Immunisation Program (NIP).

  • Schedule: Vaccines are provided free for children at 6 weeks, 4 months, 6 months, 18 months, 4 years, and 12-13 years of age.
  • Boosters: Booster doses are recommended in adolescence, during pregnancy (between 20-32 weeks), around age 50, and for adults every 10 years.
  • Coverage: Data indicates a decline in routine childhood immunization coverage since the COVID-19 pandemic. In 2025, coverage fell to its lowest level in five years. As of recent reports, 91.9% of five-year-olds in the NT are fully vaccinated against diphtheria, and 92.2% in WA.

Individuals can check their vaccination status via the Australian Immunisation Register or the myGov app. Catch-up vaccinations are free for individuals under 20 years of age.

Expert Commentary and Context

Experts have cited factors that may contribute to outbreaks.

Lower vaccination rates combined with limited healthcare access in remote areas create a significant challenge and the disease may continue to spread due to interconnected communities. – Barbara Nattabi, University of WA public health lecturer.

  • Curtin University international health professor Jaya Dantas noted that diphtheria, like other diseases, had been effectively controlled but is experiencing a resurgence. Dr. Dantas recommended reviewing the National Immunisation Program to include populations such as First Nations communities.
  • Public health physician Dr. Gary Dowse stated the reason for the Kimberley outbreak is unknown and that the disease appears to be transmitting more readily than previously understood.

Public Advice

Health authorities advise the public to:

  • Ensure vaccination status is current for both children and adults, including booster doses if recommended.
  • Seek medical attention for symptoms including persistent sore throat, skin infections, or breathing difficulties.
  • Practice hygiene measures such as hand washing and covering coughs and sneezes.
  • Properly clean and cover wounds.
  • Follow updates from local health authorities.