Yvette Anderson MPS[/caption]
Once a disease of the past, diphtheria is rapidly re-emerging across Australia. Here’s what pharmacists need to know.
What is diphtheria?
A potentially deadly and highly contagious bacterial disease, diphtheria can infect the nose and throat, cause skin sores, and spread toxin through the body; in severe cases it can cause airway blockage, heart damage and nerve damage.
Respiratory diphtheria is the more deadly variant, and is typically spread through respiratory droplets, often when people cough and sneeze. Cutaneous diphtheria can spread through touching skin sores.
What are the symptoms?
Signs and symptoms of diphtheria include:
- sore throat
- fever
- swollen neck glands
- weakness.
Post-exposure to the bacteria, symptoms typically appear within 2–5 days.
And within 2–3 days of illness onset, dead tissue can form a thick grey membrane in the respiratory tract, covering the nose, tonsils and throat, which can make breathing and swallowing difficult.
In unvaccinated people who do not receive appropriate treatment, diphtheria is fatal in up to 30% of cases.
How dangerous is the disease?
Before vaccination, diphtheria was a leading cause of childhood death in Australia. Between 1926 and 1935, there were more than 4,000 diphtheria-related childhood deaths recorded.
Once vaccination programs rolled out in the 1940s, cases of diphtheria significantly reduced.
Was it once eradicated in Australia?
Not entirely. While Australia has largely managed to control diphtheria through vaccination, surveillance data show cases continued to occur at low levels.
Until recently, there have been no recorded respiratory childhood cases since 1992. Between 2011 and 2019, 38 cases of cutaneous diphtheria were reported in both children and adults, along with seven cases of respiratory diphtheria, all in adults. Two adults who were not vaccinated against the disease died from respiratory diphtheria in 2011 and 2018.
But post-COVID-19, the disease made a resurgence – with the National Centre for Immunisation Research and Surveillance announcing in 2022 that ‘Diphtheria is back’.
Why has there been a resurgence?
Likely because vaccination coverage has declined since the COVID-19 pandemic. While Australia’s vaccination rates are still considered high by global standards, recent national data show full immunisation coverage of 91.54% at 1 year, 89.57% at 2 years, and 93.17% at 5 years of age, which is well below the 95% target in older age groups.
Can diphtheria be treated?
While diphtheria can be treated with antibiotics, they may have little effect once the infection takes hold. Another treatment, diphtheria antitoxin (DAT), can neutralise the effects of the toxin, but it needs to be administered within 48 hours of infection.
And because diphtheria had been largely eradicated, low production of DAT has led to global shortages.
Even when this treatment is administered, the Australian Centre for Disease Control has cautioned that up to 1 in 10 people with respiratory diphtheria will die.
Who is most at risk?
Children under 5 years of age are at particularly high risk of death.
Other at-risk groups include:
- those who are unvaccinated or not up to date with diphtheria boosters doses
- travellers to outbreak areas or countries where diphtheria is more common such as Nigeria, Guinea, Niger, Mauritania, Algeria, Chad, Mali, and South Africa
- immunocompromised people
- Aboriginal and Torres Strait Islander people in affected communities.
What are the risks of an outbreak here?
Pretty high when coverage is low, health experts have warned.
‘There was an outbreak of diphtheria between 2022 and 2024 in North Queensland, and also in the Kimberley in 2025,’ said Northern Territory Chief Health Officer Paul Burgess.
So far this year, more than 220 cases of diphtheria have been reported across Australia. While most cases have been recorded in the Northern Territory, the disease has spread to Western Australia, South Australia and Queensland.
Internationally, the World Health Organization reported over 29,000 suspected diphtheria cases and 1,420 deaths in the African Region from the beginning of 2025 to 1 March 2026.
How often are booster doses required?
Routine diphtheria boosters are generally recommended every 10 years for adults to maintain immunity.
For travellers to higher-risk settings, booster timing may be more frequent depending on exposure risk and destination.
What can pharmacists do?
When patients come in for routine vaccinations, pharmacists should check the Australian Immunisation Register, suggesting catch up vaccinations for children who are behind with routine immunisations, and booster doses for adults who require them. Pharmacists can also counsel patients on travel-related boosters, reminding adults that protection wanes.
‘There are new diphtheria guidelines produced by the Northern Territory government to cover this outbreak, and pharmacists need to be aware of the new guidelines,’ said Helen Stone, PSA SA & NT State and Territory Manager.
‘All frontline workers in the Northern Territory need to be protected. This includes ensuring that they’ve been vaccinated and reminding people to check their immunisation records.
‘As 69% of cases are actually cutaneous diphtheria, the message I would really like to get out is that in its early stages, the skin infection could be confused with other skin infections, e.g. a fungal skin infection. Pharmacists should be very cautious and ensure that they are referring to skin infections for further investigation, particularly in areas of the outbreak.’
