New Zealand has had 32 cases of CJD since a registry for the notifiable disease was started in 1997.
All 32 have been the sporadic form of the disease, which affects about one in a million people and accounts for up to 90 per cent of cases.
OtagoUniversity's Martin Pollock, who maintains New Zealand's registry of CJD cases, said the reason sporadic CJD developed was not known.
"It may be the normal protein undergoes a genetically induced mutation and changes shape and function. The incidence is fairly constant, at around one per million."
The case in Auckland - if it is confirmed to be CJD - will be the registry's first associated with the use of Lyodura, a German product made from brain membrane (dura) harvested from corpses.
Dr Pollock said it was used to repair gaps in the membrane caused by surgery in the brain, such as to remove a tumour.
The product was used worldwide in neurosurgery in the 70s and 80s, but was discontinued in 1987 after American neuroscientists proved a link with CJD arising from contaminated dura.
Dr Pollock said that before 1997, there were two other New Zealand cases linked to Lyodura grafts. Both involved young men.
In the first case, CJD occurred 31 months after the operation, and in the other it took 14 years to develop.
In addition, five other New Zealanders had developed the disease through the use of growth hormone treatments for short stature.
No cases of the variant version of the disease linked to eating infected meat had been recorded in NZ or Australia, Dr Pollock said.
The chances of the 43 Auckland patients who underwent surgery with potentially contaminated instruments developing CJD were "extremely remote", he said. Only eight cases from surgical instruments have been recorded worldwide since the 1970s.
