Diphtheria explained: What you need to know about the bacterial infection

Cases of diphtheria have been recorded in two children in New South Wales, prompting the state's health department to issue an alert about the disease.

So what exactly is the rare infection, which hadn't been recorded in the country since the 1990s?

Here's everything you need to know about diphtheria.

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What is diphtheria?

Diphtheria is a contagious infection caused by the corynebacterium diphtheria bacterium which predominantly affects a person's upper airways. It can affect people of any age.

The bacteria releases a toxin which spreads a membrane across the windpipe, causing breathing difficulties and, in severe cases, suffocation and death.

It can also affect the skin, heart and nervous system.

What are the symptoms of diphtheria?

The symptoms of diphtheria usually appear somewhere between two and five days after becoming infected.

They include:

• sore throat;
• swallowing problems;
• weakness;
• mild fever;
• breathing problems;
• a grey or green membrane on the throat;
• swollen neck glands.

If the infection occurs in the skin, it can lead to ulcers or open sores.

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Is there a vaccine?

Yes. Diphtheria is one of the first diseases children are vaccinated against in Australia – which is the reason we hadn't recorded any infections since the 1990s.

As of last year, 90 per cent of children aged under six have been inoculated.

The vaccine helps prevent infection, and is recommended for children as young as two months old.

In Australia, immunisation against diphtheria is only available through a combination vaccine, known as DTP. This also provides protection against tetanus and pertussis.

The federal health department recommends people in the following groups get vaccinated:

• Children aged 2 months, 4 months, 6 months, 18 months, 4 years, and between 10 and 15 years;
• Pregnant women in the third trimester of every pregnancy;
• 50-year-olds who have not been vaccinated in the past 10 years;
• People aged 65 or over who have not been vaccinated in the past 10 years;
• People travelling overseas who have not been vaccinated in the past 10 years;
• Laboratory workers who might have contact with the corynebacterium diphtheria bacterium.

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What treatments are available?

Treatment for diphtheria is generally twofold: patients are administered antibiotics and an anti-toxin.

The antibiotics kill and remove the bacteria causing the disease, while the anti-toxin stops the poison created by the bacteria from harming the patient.

Sometimes, surgery is also required to remove membrane which has formed across the throat, and other medications can be required to deal with complications and side-effects of the disease.

How does it spread?

Diphtheria transmits from person to person via airborne droplets. These are often passed on when an infected person sneezes or coughs and someone else either breathes the droplets in or touches a surface which the droplets have landed on.

Direct contact with an infected wound can also pass the disease on.

People who have the disease can be infectious for up to four weeks or even longer in some cases if they don't receive antibiotics.

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How deadly is diphtheria?

According to the World Health Organisation, between 5 and 10 per cent of people who catch diphtheria die, even if they receive proper treatment.

Without proper medical attention, that fatality rate rises even higher.

The disease used to be a major cause of death in Australia, killing more people than any other infectious disease in the early 20th century, and was a particularly common cause of childhood death up until the 1940s.

While it remains exceedingly rare here, outbreaks are more common in countries with lower rates of vaccination.

Cases globally have been on the rise, too. The WHO reported 4349 infections in 2009, but by 2019 that figure had risen to 22,986.