Salina ? Doctors don’t know how a Lucas woman contracted Creutzfeldt-Jakob disease, but they’re sure it didn’t come from eating tainted beef.

Creutzfeldt-Jakob is a rare disease that afflicts about 3,600 people each year in the United States, including two or three in Kansas, officials said. On Sunday, 62-year-old Linda Foulke died of the disease.

Doctors insist the type of CJD that killed Foulke was not the kind that results from eating beef from cattle with mad cow disease. The variant Creutzfeldt-Jakob disease, known as vCJD, has been confirmed in only 153 cases around the world — 143 of them in Britain.

“It is distinct between those two,” said Katie Hoskins, a spokeswoman for the Centers for Disease Control. “You can tell the difference between the two of them.”

News this week of the first confirmed U.S. cases of mad cow disease has prompted several countries to ban importing U.S. beef.

Foulke’s illness struck suddenly, and it confounded her doctors until one was found who was familiar with the disease. Not long after that, she was dead.

But the doctor who diagnosed the disease can’t explain how she contracted it.

That’s not sitting well with family members, who aren’t so sure the type of Creutzfeldt-Jakob disease that killed Foulke isn’t the same type that’s linked to mad cow disease.

“It’s hard to believe it happens out of the blue,” said Bill Patton, Foulke’s son-in-law. “With what we are seeing on the news in the last two days, maybe they don’t know as much as they think about the beef industry.”

Medical experts, though, are confident they can distinguish between classic CJD and the new vCJD.

The average age for victims of the classic CJD is 67, with 98 percent of victims older than 45. While it can be inherited or transmitted by corneal transplants or pituitary hormone treatments, in most cases there is no known cause, experts said.

“Eighty-five percent of the classic cases are spontaneous,” Hoskins said. “And we don’t know why.”

The new variant CJD is closely associated with bovine spongiform encephalopathy, or mad cow disease. Victims of vCJD tend to be younger — more than half under 30 .

Patton said his mother-in-law first noticed she was having difficulty maintaining her balance about three to four weeks before the diagnosis was confirmed in early December. She was sent to specialists, but none knew what was wrong with her.

Then Foulke was sent to Wesley Medical Center in Wichita, where a neurologist asked her a battery of questions before summoning Patton and his wife into the hall.

“The first thing he said was he knew exactly what was wrong with her,” Patton said. “He told me he was 100 percent sure. That’s what startled me.”

A brain biopsy was done on Dec. 8, six days after her illness was diagnosed, because the neurosurgeon had difficulty getting support staff to risk exposure to a potential case of the variant CJD.

“Any equipment used on this brain biopsy had to be destroyed,” Patton said.

The biopsy confirmed the classic Creutzfeldt-Jakob disease. Two weeks after the biopsy, Foulke was dead.

Patton said news this week of the mad cow case in Washington state has been particularly unsettling. The family still doesn’t believe the doctors’ contention that Foulke’s disease came from out of nowhere.

“From talking to my father-in-law and sister-in-law, everyone feels it must have come from somewhere,” Patton said.