More than a dozen cases traced back to Tennessee pain clinic.
A rare fungal meningitis outbreak has killed four people in five states and sickened at least 26 others.
While the outbreak is centered on an outpatient facility in Nashville, Tennessee experts say hundreds of patients across the country may have been exposed and now may be in danger.
"This is an evolving situation, and the data and materials are being continuously reviewed," says Dr. David Reagan of the Tennessee Department of Health.
What investigators do know is that the contaminated steroid came from a compounding pharmacy in the northeastern part of the United States and was sent to a number of pain clinics in 23 states across the country.
Officials are not divulging the name of the pharmacy or which clinics in which states are impacted, but infectious disease experts at the epicenter of the outbreak say the scope of the problem is wide.
"Many patients have been exposed and they're all now in the process of being contacted, they're being informed and they're being told that if they have any kind of symptom they should immediately seek medical care," explains Vanderbilt University's Dr. William Schaffner.
Those symptoms include severe headaches, nausea, stiff necks, slurred speech and even strokes.
This form of meningitis is unusual.
Vaccines don't protect against it and it cannot be spread from person to person.