Two Australian children have been hospitalised with rare cases of diphtheria of the throat.
They're the first cases reported in NSW since the 1990s and one of the pair, a toddler, is currently in intensive care.
So, what is diphtheria?
Diphtheria is a contagious bacterial infection spread easily between people through physical contact or respiratory droplets.
It has been a feared childhood disease throughout history because of devastating outbreaks.
The infection was a common cause of death in children up until the 1940s, when a vaccine was widely rolled out.
The disease occurs mainly in countries with poor levels of immunisation, NSW Health says.
It is the toxins produced by the bacteria that cause harm, says Professor Adrian Esterman, an epidemiologist at the University of South Australia.
"It's not the bacteria causing the problems it's a toxin or poison that the bacteria produces that causes problems," Professor Esterman told ABC News Breakfast.
There are two types of diphtheria, one of which affects the skin, causing skin lesions that turn into boils.
While that may sound nasty, Professor Esterman said it's much milder than diphtheria of the throat, which can be deadly.
"Then there's the throat version, which can form a membrane," he said.
"And stop the child from being able to breathe. So it can be very serious and lethal."
The toxin made by diphtheria bacteria can also cause inflammation of heart muscle and the nerves, which can be fatal in 5 to 10 per cent of people infected, NSW Health says.
What are the symptoms of diphtheria?
- The first symptoms are usually a sore throat, loss of appetite, and a mild fever.
- Within 2-3 days a membrane forms over the throat and tonsils that can make it hard to swallow and breathe.
- Can also cause the lymph glands and tissues on both sides of the neck to swell, known as "bull neck".
- Can also cause inflammation of the heart muscle which can be fatal.
- Sometimes diphtheria can cause small skin sores that form larger ulcers, commonly on the legs.
What are the treatments?
Infection can be treated with diphtheria antitoxin. Antibiotics can also be given to kill the bacteria and toxin production and prevent transmission.
If things get really bad it can be treated with surgery.
"In the case of the throat version, you can actually surgically remove the membrane," Professor Esterman said.
"And then of course we use antibiotics and antitoxins as well."
Close contacts can been given post-exposure prophylaxis, which can include antibiotics and immunisation, to reduce the risk of transmission.
The close contacts of the two NSW cases were given antibiotic therapy and anti-toxins.
Health authorities say there's no ongoing risk to the broader community.
How important is vaccination? How is it prevented?
Vaccination has prevented the deaths of countless children.
"Look, at the beginning of the 20th century, I'm talking about the 1900s, diphtheria was one of the biggest killers of children," Professor Esterman says.
"But in the 1920s, a vaccine was developed against the toxin that the bacteria produces, it was widely given out in schools in the 1930s, and ever since then diphtheria has been captured at very low numbers."
In Australia, more than 90 per cent of children are vaccinated against the disease. NSW Health says it is part of childhood immunisation.
It is given in combination with other vaccines known as DTP vaccine, which contains vaccines against diphtheria, tetanus and pertussis, also known as whooping cough.
Professor Esterman says the small percentage of children who are unvaccinated are at risk.
"But, of course, we have that very small percentage who aren't [vaccinated]," he said.
"We also have people coming in like refugees from overseas who might have it because of the sort of terrible things they have gone through in their own countries they came from.
"We have a few cases occurring in our Aboriginal communities."
Professor Esterman's message is simple.
