Non-contagious meningitis struck 14 patients -- all but one in Tennessee -- who received steroid injections, leaving two dead, according to health officials investigating the outbreak.
Thirteen of the victims -- in their late 40s to their early 80s -- received injections at a Nashville medical facility, Woody McMillin, spokesman for the Tennessee Department of Health, told CNN on Tuesday.
The 14th individual contracted the illness in an unspecified state.
"This is a serious disease," said Marion Kainer, an infectious disease expert with the state health department. "There is not a lot of experience in treating this, but we are getting the best experts together."
The U.S. Centers for Disease Control and Prevention and the U.S. Food and Drug Administration are among the agencies investigating the rare form of meningitis.
Eleven of the patients are hospitalized, McMillin told CNN.
St. Thomas Outpatient Neurosurgery Center in Nashville contacted 737 patients who had lumbar epidural steroid injections between July 30 and September 20, officials said. The facility was temporarily closed on September 20 and will remain closed until investigating authorities "are confident the current concerns have been resolved," the health department said.
Between 100 and 200 patients at Specialty Surgery Center in Crossville, Tennessee, may have been exposed or at risk because of lumbar injections during the same time period, according to McMillin.
Some of the patients may have had multiple procedures.
Meningitis is a general term for an infection or inflammatory process involving the lining of the brain and central nervous system.