Diphtheria is caused by a toxin produced by the bacterium Corynebacterium diphtheriae or sometimes, Corynebacterium ulcerans bacteria. It can infect the nose, throat and airways (respiratory diphtheria) or infect the skin (cutaneous diphtheria) or be carried in the body without causing symptoms.  

Diphtheria has been rare in Australia since the introduction of an effective vaccine, but a century ago, diphtheria was the most common infectious cause of death. 

There are diphtheria outbreaks happening in some parts of Australia, especially in regional and remote areas of Northern Territory, Western Australia and South Australia.

Diphtheria is a notifiable condition1

How diphtheria is spread

People can carry the diphtheria bacterium harmlessly in the nose and throat (‘carriers’).

Diphtheria spreads through close contact with an infected person:

  • breathing in droplets from coughing and sneezing
  • direct contact with saliva, respiratory secretions, or infected skin sores
  • contact with contaminated items articles soiled by nose and throat discharges, or by indirect contact with skin sores such as bandages, towels or utensils.

Signs and symptoms of diphtheria

There are two main forms of diphtheria: respiratory (primarily affects the tonsils, pharynx, nose and larynx) and cutaneous (skin lesions).

Milder illness is more common in persons who are vaccinated.

Respiratory diphtheria symptoms may include:

  • fever
  • sore throat
  • malaise 
  • enlarged tender neck glands
  • difficulty swallowing
  • respiratory distress such as severe shortness of breath, chest in-drawing or turning blue
  • In severe cases it causes a thick coating at the back of the throat called pseudo-membrane and makes it hard to breath or swallow.

Cutaneous diphtheria causes a non-healing ulcer of sore.

Diphtheria can affect nerves, the heart, and kidneys and cause long term damage or death.

Diagnosis of diphtheria

Diphtheria is diagnosed by testing of suitable samples including throat swabs, nasal and nasopharyngeal swabs, skin ulcer swabs and sputum. 

Incubation period

(time between becoming infected and developing symptoms)

Usually, 2 and 5 days (range 1 to 10 days)

Infectious period

(time during which an infected person can infect others)

  • the infectious period starts 7 days prior to symptom onset for respiratory cases and the date of the skin infection for cutaneous cases.
  • without treatment persons with diphtheria can remain infectious for weeks to several months.
  • respiratory diphtheria is considered infectious until completion of appropriate antibiotics and clearance testing returns a negative result and demonstration of two negative throat swabs.
  • cutaneous diphtheria is considered infectious until at least 72 hours of appropriate antibiotics, and the wound can be covered.

Treatment of diphtheria

Diphtheria is treated with antibiotics. Antibiotics may need to be started before results of the tests are available.

Severe cases need hospitalisation and diphtheria  antitoxin (DAT)

Prevention for diphtheria

  • Vaccination is the most effective protection against diphtheria. The diphtheria vaccine is administered through the National Immunisation Program. The first dose of diphtheria vaccine, in combination with other vaccines, is now recommended to be given at 6 weeks of age. For adolescents and adults, the combine diphtheria, tetanus, pertussis vaccine is preferred, if not given previously, as it provides additional protection against pertussis.
  • Hand hygiene can help to stop diphtheria from spreading, and covering your mouth and nose with a tissue or sleeve, when you sneeze or cough.
  • People with diphtheria need to be kept in isolation until they are certified to be free of the disease by SA Health's Communicable Disease Control Branch (CDCB).
  • Contacts of people with diphtheria need to be investigated for the disease, receive antibiotics and receive vaccination if required. A contact is any person who has been close enough to an infected person to be at risk of having acquired the infection from that person.
  • Family or household contacts of people with diphtheria should avoid high risk contacts until they have completed three days of antibiotics.  
  • People travelling to countries where diphtheria is common should have received a full course of immunisation and consider a booster dose of vaccine in discussion with their doctor.

Useful links

1 – In South Australia the law requires doctors and laboratories to report some infections or diseases to SA Health. These infections or diseases are commonly referred to as 'notifiable conditions'.