This week, British MP Craig Mackinlay, walked into the House of Commons on artificial feet. To a standing ovation, he raised his artificial hands in triumph.

Back in September, Mackinlay nearly died from sepsis, an often lethal immune response to an infection.

An emotional Mackinlay – who spent 16 days in an induced coma, and was given only a 5 per cent chance of survival – said he had endured “eight months of hell”.

“It is not a day I ever wanted. I would rather be sitting on the backbenches whole and complete,” he said.

“I have been through eight months of hell, had sepsis, lost all my limbs. But I am back, and that is the beauty of this place, that people will accept you, the House authorities will make sure that your return is well looked after.”

Speaking to the BBC, he said he wanted to become known as the “Bionic MP”.

Prime Minister Rishi Sunak said no one could “fail to be in awe of his incredible resilience”.

Sepsis occurs when instead of fighting an infection, the body’s immune system lets rip with inflammation that damages tissue and organs.

This is an emergency: Death is certain if the inflammation isn’t quickly contained. This is why sepsis generally must be treated in intensive care.

It can take as little as 12 hours from the earliest signs of infection to organ failure and death.

Every year in Australia there are 55,000 sepsis cases, including 8000 that are fatal. Generally, there is amputation of legs or arms in about 1 per cent of cases.

But how and why?

As inflammation moves through the body, an abnormal chain reaction of clots can form in blood vessels. This reduces blood flow to organs and to extremities.

Education and advocacy group Sepsis Network says this means nutrients cannot get into the tissues in fingers, hands, arms, toes, feet, and legs.

When the tissues are starved of oxygen and nutrients, they begin to die and this causes gangrene.

At first, the skin may look mottled, bluish purple, and then black. This dead tissue must be removed because it can cause infection to spread.

Mackinlay remembers hearing medical staff discuss his limbs.

“By then they had turned black … you could almost knock them,” he told the BBC, likening them to the plastic of a mobile phone.

If the gangrenous area is small, surgeons can try to remove just enough of the rotten tissue to stop the spread. However, if the damage is extensive, an amputation is needed.

This is a two-way street – amputations can be the result of sepsis but an amputation can also cause sepsis. This happens when a pressure injury develops from a prosthetic and becomes infected.

What are the symptoms?

It’s tricky to diagnose sepsis, because there isn’t just one symptom. Symptoms can vary but will tend to be a cluster of events.

Some can seem, initially, like a sudden onset of flu: Fever or low temperature, chills, uncontrolled shaking, tiredness and headache.

Rapid breathing, rapid heart and uncontrolled shaking can indicate something more serious is happening.

Other symptoms can include confusion or anxiety (common in older people, and can be mistaken as symptoms of dementia), nausea and vomiting, difficulty breathing, mottled skin, a sudden drop in blood pressure, drowsiness or impaired consciousness, chest pain and reduced urine.

People at high risk

People with any kind of infection, especially bacteremia (bacteria in the blood) are at high risk.

According to federal government advice, via Health Direct, others at high risk include:

• Those with weakened immune systems
• People aged over 65 years
• Pregnant or recently pregnant women
• Babies and very young children
• People with illnesses such as diabetes, cancer, AIDS, and kidney or liver disease
• People who have recently had surgery or another procedure (especially those with catheters, IVs or breathing tubes)
• People with cuts, burns, blisters or skin infections.

Post-sepsis syndrome

Many people who survive sepsis recover completely and return to normal life.

But some, especially those who spent a long time in ICU, suffer long-term physical and mental effects. This is known as “post-sepsis syndrome”.

Due to poor blood circulation, there may be damage to limbs, fingers or toes, or damage to lungs that can affect breathing.

They may suffer mental disturbances such as not being able to sleep well, nightmares, panic attacks, flashbacks or hallucinations.

Also, people with post-sepsis syndrome may feel tired all the time, or find it nearly impossible to concentrate. They may suffer a loss of confidence, and not believe in themselves. There can be brain changes that result in impaired mental functioning.