In 2015, mother-of-two Korina Valentine was sent home by a GP with suspected gastro. Four months later, she woke from a coma to find her arms and legs had been amputated.

Her doctor had failed to diagnose she had sepsis.

"The doctor just diagnosed me with gastro and sent me home to rest," she told 7.30.

It was a crucial mistake. And the next morning her husband Daniel rushed her to hospital.

"Korina could hardly walk," he told 7.30.

"I was practically carrying her through the doors of the hospital."

To save her life, doctors eventually amputated her limbs.

"If the GP had recognised the symptoms as sepsis, I am sure it would have been a lot different today," Korina said.

'I turned him over and he was unresponsive'

Sorry, this video has expired Tiffany O'Shea describes finding her young son dead of sepsis

Tiffany O'Shea's 14-month-old son, Hayden, didn't even make it to the doctor.

"I didn't know it would be something that could take a person's life so quickly," Tiffany O'Shea told 7.30.

He went to bed with a temperature and died just hours later.

"I went and checked on him at 6.30 and checked on him at 7.30," Ms O'Shea said.

"He looked up at me and I said, 'You're supposed to be asleep'.

"And then I checked on him at 8.30 and he was face down.

Tiffany O'Shea's son Hayden ( Supplied: Tiffany O'Shea )

"I thought, 'That is a very strange position', and I turned him over and he was unresponsive, you know, blue around the mouth … unlike anything I've ever seen."

Tiffany O'Shea has been through hell, she can no longer hold back her pain.

Her voice starts to break up, tears roll from her face.

"That was probably the worst thing I've ever seen in my entire being," she said.

"You don't prepare yourself to sort of see, well, even a dead person, but let alone your son, and when he's only that little.

"I just didn't know what to do.

"I shook him and it was just nothing."

Australia failing to address sepsis emergencies

Each year, the deadly disease takes 5,000 Australian lives — more than one person every two hours.

It occurs when the body's immune system overreacts to infection, injuring tissues and organs.

Prof. Simon Finfer holding up a sign campaigning for action on sepsis ( Supplied: Simon Finfer )

Yet 40 per cent of all Australians haven't even heard of the disease.

Stories like Tiffany O'Shea's and Korina Valentine break the hearts of doctors like Professor Simon Finfer.

"The problem with sepsis is that very early on, the signs and symptoms are the same as having the flu," he told 7.30.

Signs you might be developing sepsis include:

a high pulse rate

a high pulse rate laboured breathing

laboured breathing lethargy or confusion

lethargy or confusion a high or even low temperature.

The only treatment for Sepsis is antibiotics, and getting them quickly is critical to survival.

"Each hour treatment with effective antibiotics is delayed, the risk of dying increases by between 4 per cent and 8 per cent," Professor Finfer said.

"So, it is a genuine, time-critical emergency."

And with at least 18,000 people a year developing the disease, he says Australia's medical profession is failing to address that emergency.

In conjunction with the George Institute for Global Health, Professor Finfer and other medical professionals have co-authored a report calling for urgent national action to address Australia's silent killer.

Korina Valentine after having her arms and legs partially amputated due to sepsis. ( ABC News: Jerry Rickard )

"I've worked in other countries around the world, and I think Australia has one of the best healthcare systems in the world, but in this particular area, we've been failing," he said.

"We constantly hear of people who present to hospital early with sepsis.

"They appear to have the flu or a minor infection. They're sent home because they don't need admission to hospital at that time and they're not given instructions to return to the hospital if certain signs are getting worse."

That has fatal consequences.

"There are preventable deaths," Professor Finfer said.

"People are dying unnecessarily, people are having long-term healthcare problems because we have not been getting onto the treatment of sepsis as quickly as we should."