A North Carolina hospital says 18 patients were exposed to a rare and fatal brain disease after "extra precautions should have been taken, but were not."

Novant Health Forsyth Medical Center in Winston-Salem, N.C., said surgical tools used on a patient suspected of having Creutzfeldt-Jakob disease should have been subjected to "enhanced sterilization procedures" to remove CJD-linked proteins called prions. Instead, the instruments underwent the normal, less stringent sterilization process and were subsequently used in 18 neurosurgery patients, according to the hospital.

"Our standard procedure is to apply the enhanced sterilization process to surgical instruments that are used on any patient who is suspected or confirmed of having CJD in order to prevent possible transmission," the hospital said in a statement. "There were reasons to suspect that this patient might have had CJD. As such, the extra precautions should have been taken, but were not."

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 prion proteins that lead to a sponge-like pattern of holes in the brain.

Learn more about Creutzfeldt-Jakob disease.

Most CJD cases are sporadic, meaning they arise in people with no known risk factors. But 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.

"The risk to these individuals is remote," Dr. Jim Lederer, the hospital's vice president of clinical improvement, said in a statement. "However, we cannot say there is no risk and therefore it is our obligation to notify patients and provide them with information and support. Our first concern is for our patients who are recovering from surgery and may now need additional support."

CJD can be diagnosed only through an autopsy, but symptoms like memory loss, behavioral changes, lack of coordination and visual disturbances should raise red flags. Over time, these early symptoms 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 North Carolina warning comes five months after 15 neurosurgery patients were exposed to CJD in Massachusetts, New Hampshire and Connecticut.

Rare Brain Disease Confirmed in N.H. Patient, 15 Others Possibly Exposed