The incubation period is estimated at anywhere from 2 to 28 days, so some people may not have fallen ill yet, Tennessee health officials said. At three clinics in Tennessee, officials are contacting the more than 900 people who received the steroid in the past three months
Investigators have been looking into the antiseptic and anesthetic used during the injections. Neither has been ruled out. However, the primary suspicion is on the steroid medication. Steroid shots are common for back pain, often given together with an anesthetic.
The Food and Drug Administration identified the maker of the steroid as New England Compounding Center, a specialty pharmacy in Framingham, Mass. Last week, the company issued a recall of three lots of the steroid — methylprednisolone acetate. In a statement, the company said it had voluntarily suspended operations and was working with regulators to identify the source of the infection.
The outbreak was discovered about two weeks ago when Vanderbilt University's Dr. April Pettit was treating a patient who was not doing well for reasons doctors did not understand.
When the laboratory found the fungus in the patient's spinal fluid, Pettit began asking questions and learned the patient recently had steroid injections in his spine, according to Dr. William Schaffner, who chairs Vanderbilt's Department of Preventive Medicine.
"When it became clear that the infection control practices at the clinic were up to par, the steroid medication became implicated," Schaffner said.
Federal officials did not release condition reports or details on all the patients in the five states. Fungal meningitis is treated with high-dose antifungal medications, usually given intravenously in a hospital.
Seventeen of the Tennessee cases were treated at the Saint Thomas Outpatient Neurosurgery Center in Nashville. It had 2,000 vials of the suspect lots, the largest number. That clinic voluntarily closed last month to deal with the investigation.