Diphtheria

Diphtheria is caused by a bacterium, Corynebacterium diphtheriae. The bacteria produce a toxin which can have life threatening effects on the upper airway. The name comes from a Greek word relating to “leather” or “hide” which describes the membrane coating the throat. 

It is also responsible for serious systemic effects on other parts of the body. Heart and kidney damage may occur. 

Humans are the only reservoir of the disease and transmission can occur through respiratory droplet infection or via direct contact with the skin. It can also be transmitted by raw milk.

Diphtheria was a common cause of death in children prior to the 1950’s. It is now very rare. Prior to the early immunisation programs of the 1920’s, hospital mortality rates were more than 50%.  During the 1920’s the United States reported 100,000 to 200,000 cases annually with up to 15,000 deaths. It is largely eliminated now (less than 1 annually).

The low number of reported cases in Australia is largely due to our very successful national immunization program (NIP). Cases of diphtheria are more likely to enter Australia from overseas and transmission into the wider community can only be prevented by high rates of immunisation.

Recent outbreaks in Nigeria (2023) and Australia (2026) have raised media attention to this largely forgotten disease. A suboptimal immunisation rate was identified as a key contributor to the large number of cases aged 2-14 years in Nigeria. Civil disturbances impacted on vaccination programs leaving children vulnerable to the disease.  

Factors contributing to the 2026 Australian outbreak are yet to be defined.  

In 2018, a fatal case of diphtheria was reported in twenty-two-year-old female. She had not been vaccinated. The strain of diphtheria was found to be penicillin resistant. 

Diphtheria is a notifiable disease in Australia.

As of 18 May 2026, 221 cases of confirmed diphtheria have been notified this year.

The bacterium can live in the mouth of infected people. It is spread by droplet infection from person to person (coughing, sneezing). Direct spread is possible via raw milk.

Yes. It can be treated with an antitoxin. The antitoxin binds with the toxin to limit its effect on human healthy cells. It is the damage done to the cells of the upper airway which causes respiratory obstruction. This is the so called “strangling angel”. The antitoxin works like an antidote. Early treatment is necessary to avoid fatalities. 

A lack of antitoxin availability was responsible for the large number of deaths in the Nigerian outbreak.  The use of antitoxin reduces mortality by over 75%. 

Antibiotics are necessary to get rid of the bacteria producing the toxin. The antibiotics reach various parts of the body where the bacteria are found. Antibiotics generally render the individual non-infectious within 2 days. A full course of antibiotics is given over 14 days. Eradication is confirmed by nasopharyngeal swab culture. Emerging antibiotic resistance is an issue. 

Antibiotics have no effect on the toxin. 

Contacts of a case are monitored for illness, and swabs are taken from the upper airway. A vaccine booster is given if they are not up to date. Health Departments have the right to pursue contacts of cases.

Primary prevention is by vaccination. Diphtheria is a component of the Infanrix hexa, or Vaxelis vaccine. It is given in the first year of life. A child is born with the mother’s immunity and this wanes over time. Doses of the vaccine are given at 2, 4 and 6 months with a booster of a diphtheria containing vaccine at 4 years. This provides the child with their own immunity.

It is also a component of the triple antigen (diphtheria/tetanus/pertussis, dTpa). This is often given after an injury (for the tetanus component) or in the 3rd trimester of pregnancy (for the whooping cough component). These “other doses” help to keep the community herd immunity high, locking out potential transmission.

Individuals are often reminded to review their routine immunisations when travelling. A common one is tetanus. It is fortunate that diphtheria, tetanus and whooping cough can all be updated in one vaccine (Adacel, Boostrix).

Diphtheria is also available in combination with tetanus, whooping cough and polio (Adacel polio, Boostrix IPV) and might be considered for travellers to regions where vaccine associated polio is being reported.

Not sure if your triple antigen is up to date? Speak with one of our experienced Australian travel doctors via telehealth. We can review your immunisation history and recommend any boosters you need before you go. Book a consultation.

Elisha Graves Otis, the founder of Otis Elevator Company, died of diphtheria in 1861. American presidents have also had children who have died from diphtheria (Grover Cleveland (1904) and James Garfield (1863)).