Eleven patients who had brain surgery at a Greenville hospital are being warned they might have been exposed to a rare, fatal brain disease.

A patient who had surgery in February at the Greenville Hospital System was later diagnosed with Creutzfeldt-Jacob disease, potentially exposing the 11 people who had surgery afterward, the hospital said Tuesday.

Workers sterilized the instruments after every surgery, but the Centers for Disease Control and Prevention recommends additional cleaning if Creutzfeldt-Jacob disease is suspected. The disease can only be verified through an autopsy or brain biopsy.

The disease only affects about 300 people in the United States annually, and there has never been a case involving transmission through surgical instruments, according to the CDC.

But hospital officials said they wanted to warn patients out of an abundance of caution.

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"This is a very unusual event. After a full assessment and discussion with the CDC, we believe the risk of transmission of Creutzfeldt-Jacob disease to any patient is extremely small. We also value transparency and thus notified all patients who could be affected by this potential exposure," Dr. Thomas Diller, Greenville Hospital System's vice president of quality and patient safety, said in a statement.

Most reported cases of Creutzfeldt-Jacob disease happen spontaneously, when an agent causes proteins in the brain to fold incorrectly. About 10 to 15 percent of cases involve a genetic mutation that is passed down among families, according to the Creutzfeldt-Jacob disease foundation.

The disease causes behavior changes, memory loss, falling down and other impaired coordination. It is always fatal, with patients dying within a year of showing symptoms.