(WASHINGTON) -- Two more people have died from fungal meningitis linked to tainted steroid injections, raising the death toll for the outbreak to 23.
Over the weekend, the U.S. Centers for Disease Control and Prevention increased the tally of cases to 297 -- 294 cases of fungal meningitis and three cases of joint infections. The growing outbreak, which spans 16 states, has been linked to contaminated vials of methylprednisolone acetate, an injectable steroid used to treat back and joint pain.
Sealed vials of the steroid, made by the New England Compounding Center in Framingham, Mass., contained Exserohilum rostratum, a fungus found in soil and plants. It's unclear how the fungus landed in the sealed vials.
The CDC has confirmed 26 cases of Exserohilum meningitis, as well as one case each of Aspergillus and Cladosporium meningitis.
The New England Compounding Center has recalled all its products and shut down operations. Calls to the owners were not immediately returned.
As many as 14,000 patients are thought to have received injections of the suspect steroid.
Seventy-six clinics in 23 states that received methylprednisolone acetate from the recalled lots have been instructed to notify all affected patients. The "potentially contaminated injections were given starting May 21, 2012," according to the CDC.
Meningitis affects the membranous lining of the brain and spinal cord. Early symptoms of fungal meningitis -- including headache, fever, dizziness, nausea, sensitivity to light, stiff neck, weakness or numbness, slurred speech and pain, and redness or swelling at the injection site -- can take more than a month to appear.
The longest duration from the time of injection to the onset of symptoms in the current outbreak is 42 days, according to the CDC's Dr. Benjamin Park.
"But we want to emphasize that we don't know what the longest will be," he added, stressing that patients who received injections of the recalled drug should stay attuned to the subtle symptoms "for months."
Fungal meningitis is diagnosed through a spinal tap, which draws cerebrospinal fluid from the spine that can be inspected for signs of the disease. Once detected, it can be treated with high doses of intravenous antifungal medications.
Unlike bacterial meningitis, fungal meningitis is not transmitted from person to person and only people who received the steroid injections are thought to be at risk.
Copyright 2012 ABC News Radio