Very few infectious diseases are fully eradicated. We think of smallpox (which has been eradicated) and often think we are very clever and can do the same with many other diseases. It isn’t that easy.

An outbreak of diphtheria in Africa is a good reminder. As of January 2024, almost 28,000 cases and 828 deaths have been reported across Nigeria, Guinea, Mauritania, and South Africa. More than 80% cases come from Nigeria. According to the report, only 24% cases were fully vaccinated with 70% under the age of 15 years.

Outbreaks of vaccine preventable disease are often a reflection of the impact of vaccine shortages, armed conflict, and poverty on vaccination programs.

What is diphtheria?

Diphtheria is caused by a bacterium, Corynebacterium diphtheriae. The bacteria produce a toxin which can have life threatening effects on the upper airway. It is also responsible for serious systemic effects on the body. These include myocarditis, and kidney damage.

Diphtheria was a common cause of death in children prior to the 1950’s. It is now very rare because of our very successful national immunization program (NIP). No cases have been reported in the last 12 months and only an average of 3 over 5 years. This is a remarkable achievement.

How is diphtheria transmitted?

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 a possible and also via raw milk.

Can it be treated?

Yes. It can be treated with an antitoxin to limit the effect on the airway obstruction. It is like an antidote. Post infection 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 noninfectious within 2 days. A full course of antibiotics is given over 14 days. Eradication is confirmed by nasopharyngeal swab culture.

How is it prevented?

Primary prevention is by vaccination. Diphtheria is a component of Infanrix hexa, or Vaxelis vaccine which 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 a 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/ diphtheria). 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.

Cases of diphtheria are more likely to enter Australia from overseas and this is where secondary prevention is necessary. Contacts of a case are monitored for illness and swabs are taken from the upper airway. A booster is given if they are not up to date. Health Departments have the right to pursue contact tracing.

Diphtheria is a notifiable disease in Australia.