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Diphtheria’s recent resurgence in Australia

With diphtheria hitting the headlines recently, thanks to a rise in cases nationally to the highest level in decades, we thought we’d take a closer look at this deadly disease and what’s driving its resurgence in Australia.

What is diphtheria?

Diphtheria is an infection of the throat or skin caused by certain strains of the Corynebacterium bacteria, which produce a toxin that can lead to severe illness and damage to the heart, kidneys and brain.

It spreads through close contact with an infected person and can be passed on through respiratory droplets (i.e. via coughing or sneezing) or by touching infected lesions.

Respiratory diphtheria is the most severe type of infection and can be fatal, particularly for infants. According to the Western Australian Department of Health, around 5-10% of severe cases are fatal, even with treatment.

People with diphtheria can spread the infection even before they present with any symptoms.

Symptoms

Symptoms will vary, depending on whether the disease is respiratory or cutaneous.

The main symptoms for respiratory diphtheria include:

  • Cold-like symptoms, such as sore throat, fever, and chills
  • A thick, greyish-white coating in the back of the nose or throat
  • Difficulty breathing or swallowing
  • Swollen, painful glands in the neck

The main symptoms of cutaneous diphtheria, include:

  • An infected cut or wound
  • Sores or ulcers that are slow to heal, and are often on the legs
  • Sores or ulcers covered with a grey, moist scab

Diphtheria is confirmed by laboratory testing of a swab from your throat or skin sore.

If you do have any of the above symptoms, please see a doctor as soon as possible. If you experience a sore throat with fever and difficulty breathing or swallowing, seek urgent medical assistance.

Treatment

Diphtheria is treated with antibiotics. Those with the respiratory form of the disease may also require treatment with an anti-toxin to help kill the bacteria and stop the production of toxins.

As it is highly contagious, those infected will need to isolate until they are no longer infectious.

Diphtheria in Australia

As noted by the Australia Institute of Health and Welfare, the early 1900s saw high numbers of cases in Australia, resulting in a record 898 deaths in 1921.

This prompted the introduction of a widespread, school-based vaccination program in 1932.

Figure 1: Reported deaths from diphtheria in Australia (1907-2024)

Since the introduction of the vaccine program, the incidence of diphtheria has declined and, up until recently, it has remained rare in Australia with most cases originating from overseas.

In recent times, however, there has been a resurgence of the disease through locally acquired outbreaks. This has prompted Australia’s Chief Medical Officer, Professor Michael Kidd AO, to declare diphtheria a Communicable Disease Incident of National Significance.

Since an initial outbreak in the Northern Territory in late 2025, locally acquired cases have spread to parts of Queensland, South Australia, and Western Australia, including one death reported in May 2026.

As noted by the Australian Centre for Disease Control, there have been 288 reported cases of diphtheria in Australia so far this year. This includes 168 in the Northern Territory, 111 in Western Australia, 6 in South Australia, and 3 in Queensland.

These outbreaks have mostly occurred in Aboriginal communities exposed to overcrowded living conditions and reduced vaccination coverage – both of which allow the disease to spread more easily.

The decline in vaccination coverage since the COVID pandemic, particularly for childhood related diseases, has led to a reoccurrence and increase in diseases such as diphtheria and measles in recent years.

Australia has a herd immunity target of 95% immunisation coverage for these preventable diseases. According to the National Centre for Immunisation Research and Surveillance (NCIRS), routine childhood immunisation coverage fell in 2025 to its lowest level in five years, with only 90.5% coverage amongst 12 month olds, and 88.4% coverage for two year olds.

Figure 2: Reported cases of diphtheria in Australia (2015-2026)

Prevention

These recent outbreaks are a good reminder about the importance of immunisation to protect not only yourself, but the whole community.

Vaccination remains the most effective protection against severe illness from diphtheria.

The diphtheria vaccine forms part of the National Immunisation Program (NIP) Schedule and is given with vaccines for tetanus and pertussis (dTpa) to:

  • Infants – at 6 weeks, and at 4, 6 and 18 months
  • Children – at 4 years
  • Adolescence – in year 7 at school, with a catch-up dose available up to 20 years, for those who miss their year 7 vaccination
  • Pregnancy – ideally between 20 and 32 weeks’ gestation for each pregnancy

As immunity wants over time, booster doses are recommended every 10 years, particularly for those aged 50 years and over. Booster doses are available through private prescription.

Other ways to help reduce the spread of disease include:

  • covering your mouth and nose when coughing or sneezing
  • throwing away used tissues in the bin
  • washing hands regularly with soap and water, especially before preparing food, after coughing or sneezing, and before and after touching skin sores or dressings
  • keeping sores and wounds clean and covered, such as with dressings or large band-aids
  • getting skin conditions like ringworm (tinea), eczema, and scabies treated early – healthy skin helps prevent infection
  • avoiding close contact with people who are unwell
  • staying home if unwell and limiting contact with others

Vaccinations at IMC

All recommended NIP vaccines, including diphtheria, are available at Illawarra Medical Centre.

To book in for your vaccine or discuss any questions or concerns you may have, book an appointment with one of our GPs. Bookings can be made online or by contacting us on (08) 9208 6400.

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