Health officials have confirmed that a New Hampshire man who died in August following neural surgery had a rare, degenerative brain disease, raising alarms for 15 other patients who may have been contaminated by the same instruments.

Autopsy results showed the unidentified man, who underwent surgery in May at Catholic Medical Center in Manchester, N.H., had contracted sporadic Creutzfeldt Jakob disease - a degenerative brain disorder spread by infected brain tissue and cerebrospinal fluid and is characterized by rapidly progressive dementia.

Sporadic CJD is different from the human form of "mad cow disease," dubbed bovine spongiform encephalopathy, which is acquired through eating contaminated beef.

"Though we are not surprised by the test results, we are saddened by the toll this disease takes on families and our sympathies go out to all those affected," said Dr. Jose Montero, New Hampshire's director of public health, in a statement.

"Our focus and concern continues to be with the patients who may have been exposed to CJD," said Dr. Joseph Pepe, president and CEO of Catholic Medical Center.

Earlier this month the New Hampshire Department of Health and Human Services contacted eight patients who may have been exposed to the rare brain disease after undergoing neurosurgery that used shared hospital equipment. The patients have since been notified on the positive autopsy results.

An additional five patients in Massachusetts and two in Connecticut who underwent surgery using the same potentially contaminated equipment were also warned of the risk of possible exposure.

"The risk to these individuals is considered extremely low," Montero, said in an earlier statement. "But after extensive expert discussion, we could not conclude that there was no risk, so we are taking the step of notifying the patients and providing them with as much information as we can. Our sympathies are with all of the patients and their families, as this may be a confusing and difficult situation."

Although surgical equipment is routinely sterilized, the proteins that cause the disease can survive such procedures. Symptoms may not reveal themselves for years and diagnosis can only be determined through autopsy.

"The risk of contracting CJD from a surgical instrument is extremely low," the Massachusetts Department of Public Health said in a statement. "There have been only four confirmed cases in the world, and none of these cases occurred in the U.S."

Creutzfeldt-Jakob disease, or CJD, is extremely rare, affecting one in a million people worldwide per year, according to the National Institutes of Health. It's believed to be caused by abnormal proteins called prions that lead to a sponge-like pattern of holes in the brain.

Most CJD cases are sporadic, meaning they arise in people with no known risk factors. Up to 10 percent of cases are hereditary, according to the NIH, and 1 percent of them are acquired through contact with contaminated brain tissue.

Early symptoms of the disease include memory loss, behavioral changes, lack of coordination and visual disturbances, which give way to involuntary movements, blindness, weakness and coma. There's no cure, and about 90 percent of patients die within a year, according to the NIH.

The surgical equipment used on the suspected CJD patient was made by Medtronic, a company that makes tools for neurosurgery.

Medtronic, however, indicated that its equipment was not used on all 15 patients. The company said that when it was informed "that our instruments had been used in this case, we followed procedures to quickly track that specific set of instruments and have confirmed they were used in seven additional cases. We are assisting the hospitals and the appropriate state health authorities as they manage this situation."

The Massachusetts Department of Public Health claims in its statement that the "general public and any other patients at CMC and their employees are not at any risk."

ABC News' Katie Moisse contributed to this report.