A "Diphtheria tent" from Swan Hill Hospital. Photographer: George Hamilton, active 1905-1917 Image source: State Library of Victoria

The return of a nearly forgotten disease: diphtheria reported in NSW

Introduction by Croakey: Reports of two cases of diphtheria in northern NSW have raised concerns among doctors and public health experts, even drawing the attention of the Director-General of the World Health Organization, Dr Tedros Adhanom Ghebreyesus.

Below, Associate Professor Frank Beard and Professor Kristine Macartney of the University of Sydney and Noni Winkler of the Australian National University brief on this potentially deadly disease and outline the important role vaccinations play in preventing its spread.

This piece originally appeared in The conversation and has been reposted here with permission.

Frank Beard, Kristine Macartney and Noni Winkler write:

An unvaccinated toddler from the far north coast of New South Wales has arrived intensive care after contracting respiratory diphtheria (diphtheria of the throat). A six-year close family contact is also infected.

These are the first cases of respiratory diphtheria in children in Australia since 1992

What is diphtheria and how is it spread?

Diphtheria is a potentially fatal infection caused by toxins produced by certain strains of Corynebacterium bacteria.

Respiratory Diphtheria Causes severe swelling of the throat and neck, which can block the airways and cause difficulty breathing.

The bacterial toxin can also damage the heart, kidneys, brain and nerves. The bacteria can also cause: skin ulcerswhich are not as severe as respiratory diphtheria.

The diphtheria bacteria spread through air droplets, for example by coughing or sneezing. They can also spread by touching skin sores.

Australia’s Vaccination Program

In Australia, vaccines containing diphtheria toxoid (an inactivated form of the toxin) are distributed free of charge on the National vaccination program (NIP), with three doses initially at two, four and six months of age.

These are six-in-one combination vaccines that also protect against whooping cough (whooping cough), tetanus, polio, hepatitis B, and Haemophilus influenzae type b (Hib) infection, which causes meningitis (inflammation of the lining of the brain) and septicemia (septicemia).

Booster doses for diphtheria, tetanus and pertussis are provided under the National Immunization Program at 18 months, four years and around 12 years (through school-based immunization programs). It is important to get all of these booster doses as immunity wanes over time.

Boosters for adults are also recommended, but are not funded by the National Immunization Programme.

Treatment options

Antibiotics are given to people with diphtheria but may not have much of an impact on the disease once diagnosed.

Specialized treatment with diphtheria antitoxin (DAT) is often needed to counteract the effects of the toxin. DAT should be given early in the illness (within 48 hours).

However, there are global shortages of DAT due to reduced production in recent decades.

A historical perspective

Diphtheria was once one of the top ten causes of dead child† There were more than 4,000 dead of diphtheria in Australia between 1926 and 1935.

Diphtheria cases dropped dramatically after the introduction of vaccines in the 1940s.

Diphtheria is now rare. Prior to the two recent cases in NSW, there had been no cases of childhood respiratory diphtheria in Australia since 1992. Between 2011 and 2019, 38 cases of skin diphtheria were reported, in both children and adults. During the same period, there were seven cases of respiratory diphtheria, all in adults. Two unvaccinated adults died of respiratory diphtheria in 2011 and 2018

Why Are Cases Occurring Now?

Anyone who has not been vaccinated against diphtheria is at risk of disease. Vaccination coverage against diphtheria in Australian children has been high at over 90% since 2000 and is currently around 95%

People born before 2000 are more likely to be undervaccinated because vaccination rates were lower when they were growing up.

There is also a particular risk of traveling to countries where diphtheria is more common, including Southeast Asia, Papua New Guinea, states of the former Soviet Union and Eastern European countries.

Diphtheria vaccination prevents disease, but does not completely prevent people from carrying the bacteria in the back of their throats without symptoms. It is possible for fully vaccinated people to spread the bacteria to unvaccinated contacts, even when returning from a foreign trip.

Increases in diphtheria now pose a real risk, as does vaccination coverage declined worldwide

We are also at an increased risk of other illnesses, such as measles, now that international travel has resumed. Measles cases have risen worldwide, in part due to: COVID pandemic-related disruption to routine vaccination programs in many parts of the world. UNICEF and the World Health Organization warned of a perfect storm of conditions for the measles outbreak.

A recent case of measles in a traveler was the first in Australia since March 2020.

Take action

Making sure people of all ages are up to date on their vaccines is critical.

Parents should ensure that children receive all their routine vaccinations on time – this will provide strong protection against serious illnesses such as diphtheria and measles.

People of all ages should also be aware of vaccines, especially when traveling abroad. Beyond childhood, the Australian Immunization Handbook recommends a diphtheria vaccine booster dose for:

  • adults aged 50 and 65
  • people of all ages who are more than ten years since their last dose and who are traveling to a country where health services are difficult to access.
  • people traveling to high-risk countries if the last dose was more than five years ago.

Ensuring support for low- and middle-income countries, especially those in our region, to bolster their immunization programs, including through measles catch-up campaigns and other vaccines, is also essential to protect us all.

To see here for Croakey’s archive of immunization stories

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