60 Minutes: The flesh-eating superbug that nearly killed Sam O'Sullivan.

Imagine waking up one morning to discover that a superbug has wormed its way into your immune system.

Imagine discovering that the same superbug – with no known cause and no known cure – was at that very moment attacking your flesh, and that your chances of survival were slim to none.

That’s the situation football player Sam O’Sullivan found himself in. And on tonight’s 60 Minutes, Sam’s extraordinary story of survival was revealed.

Sam went to bed healthy one night, and woke up the next morning with crippling pains in his shins – a sensation doctors later realised was the superbug beginning to tear at the muscles of his legs. 

At first, doctors at Melbourne’s Box Hill Hospital couldn’t diagnose what was causing Sam’s pain. Dr. Lin-Li Lim, a specialist in infectious diseases, says he knew something was seriously wrong when Sam failed to respond to anitbiotics after 24 hours of treatment.

With Sam’s leg swelling and a concerning rash spreading across his body, his doctors had no choice but to perform explorative surgery. What they found was necrotising myositis, a rare and deadly diseased that had already laid most of the muscles in Sam’s right leg to waste.

Sam was placed into an induced coma, and underwent six further operations over the course of ten days. As the bug spread, surgeons were forced to hack away more and more of the dead tissue in his leg. The chances that Sam would live were slim - and doctors were careful to inform Sam's parents that, if he did survive, it would likely be at the expense of his leg.

"I just kept thinking, 'OK, let’s just forget about everything else, don’t worry about the amputations. Don’t worry about the not playing footy.' The main focus at that point was to just for him to survive, for him to live, and that is what we had to focus on," Sam's mother Mary told 60 Minutes.

In the end, it took almost one hundred doctors to save Sam's life.

Watch the preview for tonight's 60 Minutes. Post continues after video... 

The first thing he said when he awoke was, "Mum, what the eff?"

For someone who has spent his life running and jumping, seeing his wasted leg came as an enormous shock to Sam.

"I’m going, 'Hang on... I’ve been told I’m not going to play footy again? I’m not going to walk again?' Like, I was just, like, 'Are you kidding me?' Like, 'Surely you’re joking.' I just, I couldn’t comprehend what had just happened," he told 60 Minutes.

Since that terrible week, Sam has had further operations to increase the movement in his leg - and he's trying hard not to let himself be restricted.

"We did laugh in hospital when they said he won’t be walking for, you know, two weeks, and Joss and I both went, 'Yeah, I’ll give it two days,' and you were literally up in two days," Mary says affectionately to her son.

Of course, the shock of such a sudden and terrifying illness has left its mark, but Sam is working hard to work through his demons.

"I did certainly have down days where I just think I couldn’t go on but, you know, there’s always a light at the end of the tunnel. There’s always something that you can positively change."