Last updated:
Disease groups:
At a glance
- Vaccine preventable – check who’s eligible
- Vaccine included on the National Immunisation Program – check who’s eligible
- Nationally notifiable disease
About diphtheria
Diphtheria is caused by toxin-producing Corynebacterium diphtheriae or, rarely, Corynebacterium ulcerans bacteria.
The bacteria can:
- infect the nose, throat and airways (respiratory diphtheria)
- infect the skin (cutaneous diphtheria)
- be carried in the body without causing symptoms.
The bacteria can also make toxins, which lead to serious complications.
Read more about diphtheria.
Why it matters to public health
Diphtheria can cause severe illness and death.
In communities with lower vaccination coverage, diphtheria can cause more serious illness and spread more easily. Before routine vaccination, diphtheria was a common cause of death in children in Australia.
Diphtheria is now uncommon in Australia, but recent outbreaks in some remote and regional parts of the Northern Territory, Western Australia and South Australia have led to a sharp increase in infections since late 2025. Public health efforts are focused on providing vaccinations to people in affected areas.
Symptoms
If you’re looking for advice about your own health or treatment options, see healthdirect or speak with a qualified healthcare professional. Our role is to provide public health advice – information and guidance that helps prevent disease, protect communities and improve wellbeing at a population level.
Symptoms depend on where the infection happens in the body – either the respiratory tract or the skin.
Respiratory diphtheria symptoms can include:
- mild fever
- a sore throat
- malaise (feeling unwell)
- loss of appetite.
Within a few days, toxin made by the bacteria can cause a greyish-white membrane to form in the throat. This can lead to serious symptoms including:
- difficulty swallowing
- difficulty breathing
- neck swelling (bull neck).
The toxin can cause myocarditis (inflammation of the heart) and paralysis (nerve damage).
Without quick treatment, respiratory diphtheria can be serious or even fatal.
Cutaneous (skin) diphtheria symptoms include:
- skin ulcers with a bluish appearance, often on the legs or arms
- infection of pre-existing skin lesions.
Cutaneous diphtheria wounds are slow to heal and become chronic if left untreated.
healthdirect’s symptom checker can help you decide whether to see a health professional.
Onset of symptoms
Diphtheria symptoms usually appear 2 to 5 days after infection but can be longer.
How it spreads
Corynebacterium diphtheriae spreads from person to person, usually after close or prolonged contact.
Spreads between people can happen through:
- the air – such as when an infected person coughs or sneezes
- secretions from the nose or throat
- fluid from skin sores.
Some people carry the bacteria in their nose or throat without getting symptoms. These people can unknowingly spread the bacteria to others and make them sick.
Although rare, the Corynebacterium ulcerans bacteria can spread from animals to people through:
- close contact with livestock and domestic pets
- consuming raw milk.
Read more about how diphtheria spreads.
Infectious period
People are thought to be infectious from up to a week before symptoms start and for up to 6 weeks without treatment.
Antibiotics can shorten this period substantially.
Prevention
Vaccination
Vaccination is the best way to protect against illness and severe complications from the diphtheria toxin.
Multiple doses and booster doses are needed to produce and sustain immunity.
Vaccination is recommended for:
- infants, children and adolescents as part of routine vaccination
- routine booster vaccination in adults, including:
- pregnant people
- some laboratory workers
- travellers to countries with limited access to health services
- older people
- people who have missed doses of diphtheria-containing vaccine.
The diphtheria combination vaccine is free under the National Immunisation Program for:
- children at 2 months, 4 months, 6 months, 18 months, and 4 years
- children at 12 to 13 years through school-based vaccination programs.
If you are not eligible for a free vaccine, you can buy one from your healthcare professional or pharmacy.
Other prevention steps
To protect others, people who are unwell or have diphtheria should:
- stay at home if unwell with cold or flu-like symptoms
- keep any sores covered
- follow the advice of their healthcare professional.
Read more about preventing diphtheria.
Priority groups and settings
Some people are at greater risk of getting diphtheria or getting very sick from it.
If you are at greater risk, it is especially important to make sure you are up to date with diphtheria vaccinations.
People at greater risk of severe disease
Diphtheria poses a greater risk of severe illness for:
- young children
- people who are unvaccinated, under-vaccinated or are not up to date with their recommended doses.
People at greater risk of exposure
People are at greater risk of being exposed to diphtheria if they:
- are in a part of Australia where there have been recent diphtheria infections
- travel to countries where diphtheria is more common
- live in crowded conditions
- live or spend time in warm, humid areas – especially for cutaneous diphtheria
- are laboratory workers who may be exposed to the bacteria.
Diagnosis and treatment
The diagnosis of diphtheria is made in a medical laboratory. A healthcare professional will collect a swab from:
- the throat or nose
- fluid from skin sores.
You can use healthdirect’s directory to find a health service near you.
If diphtheria is suspected, treatment starts straight away. Some people may be treated in a hospital.
Diphtheria is treated with antibiotics – these should always be taken as directed.
Some people with diphtheria may also be given antitoxin.
People who have not recently had a vaccination for diphtheria might be offered one.
Read more about how to manage or treat diphtheria.
Surveillance and reporting
Diphtheria is a nationally notifiable disease – these are diseases that present a risk to public health.
Health authorities in each state and territory report new cases to us daily through the National Notifiable Diseases Surveillance System.
This is part of national surveillance activities, to monitor case numbers, understand disease patterns, and risk factors.
We analyse the data and publish case numbers and other data through our data visualisation tool, where you can filter and search the latest information.
Read more about the epidemiology of diphtheria in Australia.
Outbreaks
Public health units might respond to a diphtheria outbreak by:
- advising infected people to avoid group settings such as work, school and childcare until they are no longer infectious
- ensuring appropriate treatment for infected people
- cover infected sores, if relevant
- identifying and testing close contacts
- ensuring preventive treatment or vaccination, if needed
- providing information to people about the disease.
Read more about how the Australian Government defines and plans for outbreaks and pandemics.
Support
For information about diphtheria in each state or territory, see:
- Australian Capital Territory
- New South Wales
- Northern Territory
- Queensland
- South Australia
- Tasmania
- Victoria
- Western Australia.
If you need mental health support, see a list of organisations, websites and services that offer support, counselling and information.
For travel advice, see Smartraveller.