The U.S. Centers for Disease Control and Prevention today increased the tally of cases in the multistate outbreak to 424: 414 cases of fungal meningitis and 10 joint infections. At least 31 people have died.
For a map of cases by state, click here.
The outbreak 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.
For a full list of clinics receiving the recalled lots of spinal steroid injections, click here.
It's not clear how the fungus landed in the pharmacy's ostensibly sterile vials, some of which were shipped to clinics without sterility testing, according to an inspection by the Massachusetts Department of Public Health. Floor mats near sterile drug-mixing areas were "visibly soiled with assorted debris," and a leak from a nearby boiler created an "environment susceptible to contaminant growth," according to the report.
Unlike drug manufacturers, which are regulated by the U.S. Food and Drug Administration, compounding pharmacies are overseen by state boards of pharmacy. The director of the Massachusetts pharmacy board, James Coffey, has been fired for ignoring a July 2012 complaint that the New England Compounding Center was violating its license by shipping drugs in bulk, the Associated Press reported today. The board's attorney, Susan Manning, has been placed on administrative leave.
A congressional hearing on the outbreak is scheduled for Nov. 14.
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 CDC initially said the risk of meningitis was highest in the 42 days following the injection -- a six-week stretch that theoretically ended today, since the suspect steroids were recalled Sept. 26. But new cases will continue to trickle in, according to the agency.
"Forty-two days is not a magic number by any sense of the word," said Dr. Tom Chiller, a fungal disease expert at the CDC. "This is a moving target. The outbreak is evolving."
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.
ABC News' Sydney Lupkin contributed to this story.