FOUR suspected cases of the human variant of mad cow disease, one of them fatal, have emerged in western Canada, local media reports say. The degenerative brain disease Creutzfeldt-Jakob is so rare that it is odd for four suspected cases to crop up at once, CBC News quoted British Columbia Provincial Health Officer Perry Kendall as saying. There are two strains of the disease, and one is linked to infected cows. But Kendall said the four cases diagnosed in the Fraser Valley area east of Vancouver were not believed to stem from eating tainted beef. "I would not worry about this being the beef-associated variant," Kendall said. British Columbia gets five to six reported cases a year, he added. 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.