Frank Burton, a former financial officer of the Sydney Swans, has been given only weeks to live after being diagnosed with the rare, degenerative brain condition sporadic Creutzfeldt-Jakob Disease (CJD).

Peter Kogoy, a close friend of 63-year-old Frank Burton, has told the ABC Mr Burton has developed CJD, a one-in-a-million chance in Australia.

CJD has been likened to mad cow disease.

Mr Burton was the financial officer and treasurer of the Sydney Swans in the 1980s and 1990s and is described by Mr Kogoy as a "whizbang with numbers" and "life-long Bloods supporter".

Royal Prince Alfred Hospital has confirmed it is caring for a patient with the disease and said the patient's condition poses no risk of infection.

According to NSW Health, sporadic CJD is a rare, degenerative disease of the brain that is not linked to the consumption of meat and occurs in one in a million people per year in Australia.

It has no treatment or cure and the disease is fatal within weeks or months after the onset of symptoms.

Former sports journalist Mr Kogoy said Mr Burton was told on Friday he had three months to live, but now that time frame has been accelerated to two or three weeks.

He said Mr Burton was diagnosed "with something unusual" by his doctor just over five weeks ago and that there was a rapid progression of the disease.

And subsequent tests revealed it was sporadic CJD.

"[He has gone] from having a head of dark, straight [hair] and black beard, to totally white, totally white," Mr Kogoy said.

"A total loss of speech and total loss of movement in his limbs in a matter of weeks and days."

Mr Kogoy said current board members of the Sydney Swans had visited Mr Burton at an isolation wing of the Royal Prince Alfred Hospital.

"He cracked the biggest smile we've seen from him in a long time ... when we let him know that the Swans won their game last Thursday night at the SCG where he would've been there as normal," Mr Kogoy said.

"He's been a life-long Bloods supporter from day one."

Mr Kogoy said Mr Burton's close friends and family were at his bedside.

"He's fighting this to the bitter end," he said.