The fifth suspected victim in the same underpopulated area of Idaho, died of Creutzfeldt-Jakob Disease (CJD), a rare brain-wasting disease that typically afflicts only one in a million people.

"Is what is happening in Idaho an anomaly, a statistical fluke? That is possible," said Ermias Belay, a top CJD expert with the Centers for Disease Control and Prevention in Atlanta who is helping advise officials in Idaho. "But once it exceeds 1.5 or 2 per million, you start asking questions."

At the end of May local health officials saw a second elderly woman die of the incurable disease involving a malformed protein, or prion, that kills brain cells.

After that, they learned of three other suspected cases, including a CJD death in February that was reported only last month.

CJD is the human form of mad cow disease.