Alzheimer’s disease is approaching what could be a “perfect storm” of a national crisis, one expert says.

There has been an epidemic rise in the number of cases of Alzheimer’s, with the number affected growing by 500,000 in the past 5 years to an estimated 4.5 million to 5 million people, notes David Shenk, author of “The Forgetting. Alzheimer’s: Portrait of an Epidemic.”

With the front edge of the boomer generation approaching age 65, that number could mushroom to 15 million by 2011, he warns.

Speaking at a media teleconference sponsored by MetLife Foundation, Shenk warned that the crisis could be worsened by widespread ignorance about the disease. That fact was emphasized by a new Harris Poll survey, released during the teleconference by MetLife, showing 74% of Americans admitted knowing little or nothing about Alzheimer’s. Yet 35% knew someone who had the disease, the survey found.

At the same time, Americans fear Alzheimer’s more than any disease save cancer, the same survey found. That fact could add to the gathering crisis, Shenk said.

“Almost everyone is so terrified of the disease but too afraid to learn about it,” he said. “Yet it’s possible to explain in a few minutes. That knowledge goes a tremendous distance in helping caregivers plan and care for the disease. Alzheimer’s affects not only the patient but also caregivers. It can take people’s lives over for a decade or more.”

Because so few understand the disease, there are not enough people pushing for critical resources needed to provide care and to cure it, Shenk observed.

MetLife’s survey found while 80% of Americans think it’s important to plan for the possibility of getting Alzheimer’s, almost 90% have not actually taken steps to do so either for themselves or their family.

Specifically, 83% had made no financial arrangements for the eventuality, 64% had not spoken to their family about it and 58% had not designated someone to take care of their affairs if they ever got Alzheimer’s. In fact, just 26% have actually looked at their care options if the disease struck.