Frank Burton, 63, has been in a serious condition at the Royal Prince Alfred Hospital with the fatal Creutzfeldt-Jakob Disease (CJD) for the past several weeks. 

Mr Burton, a former financial officer of the Sydney Swans, was diagnosed with the rare, degenerative disease when he presented at the hospital after falling on a footpath in May, but his condition was made public only on Tuesday.

Contrary to other media reports, CJD is not highly contagious and a spokesman at the hospital has stressed the case posed no risk of the infection being transmitted.

The disease is not an airborne contagion and cannot be caught via casual human contact. Only exposure to brain tissue and spinal cord fluid from infected individuals poses a potential risk.

Mr Burton's friend, Peter Kogoy, told Network Ten news that treating doctors had no idea how he contracted the disease.

CJD is part of a group of diseases known as transmissible spongiform encephalopathies (TSEs) or prion diseases, which infect the brains of sufferers. 

Mad cow disease is also a type of TSE, known as bovine spongiform encephalopathy, which manifests as "variant" CJD in humans.

There is no cure for CJD and most sufferers die within six months of showing symptoms that are characterised by dementia and walking difficulties.

"He can't dress himself, he can't feed himself and is in need of 24/7, seven-day-a-week care," Mr Kogoy told Network Ten News.

It is estimated the chances of contracting CJD is one in one million, translating to 20 cases diagnosed in Australia each year.

The disease most commonly affects people aged between 50 and 70.

The patient's family has asked for their privacy to be respected.