Local media says four suspected cases of the human variant of mad cow disease, one of them fatal, have emerged in western Canada.
CBC News quoted British Columbia Provincial Health Officer Perry Kendall as saying the degenerative Creutzfeldt-Jakob disease is so rare that it is odd for four suspected cases to crop up at once.
There are two strains of the disease, and one is linked to infected cows.
But Kendall says the four cases diagnosed in the Fraser Valley area east of Vancouver are NOT believed to have stemmed from eating tainted beef.
One of the patients has died and a sample of brain tissue is being analysed.
The diagnosis on the other three can only be made post-mortem.