Minnesota health officials and two Twin Cities clinics are trying to track down hundreds of patients who received an injectable steroid linked to a nationwide outbreak of fungal meningitis.

No cases of the disease have been reported in Minnesota, but the outbreak has sickened at least 35 people in six states, killing five.

"Given how rapidly this investigation is unfolding, I would not be surprised if we have cases," state epidemiologist Dr. Ruth Lynfield said Thursday.

The potential scope of the national outbreak widened dramatically Thursday as health officials warned that hundreds, perhaps thousands, of patients could be at risk. The U.S. Food and Drug Administration urged doctors not to use any products from the Massachusetts pharmacy that supplied the suspect steroid.

Patients in Minnesota could have received the product from two clinic groups: Medical Advanced Pain Specialists, with offices in Edina, Fridley, Shakopee and Maple Grove; and the Minnesota Surgery Center, which is based in Edina and Maple Grove.

About 600 patients locally received epidural, or spinal, injections -- the kind linked to the national outbreak. But several hundred more received injections in other parts of the body, Lynfield said.

She said the clinics are contacting all patients who received the medication.

The steroid -- methylprednisolone acetate -- is used to treat chronic pain.

The steroid and other products made by the New England Compounding Center in Framingham, Mass., are now subject to a national recall.

Lynfield said the exact nature of the problem remains unclear. Some of the sickened patients show clear signs of fungal infections, while others have infections of unknown origins. It is possible that the steroid product was tainted with multiple germs, she said.

Patients who received the injections are encouraged to notify their doctors if they are experiencing even mild symptoms, which can include headaches, nausea, dizziness and fever. Some patients infected in other states also experienced slurred speech and difficulty in walking or urinating, according to officials in Tennessee, where three deaths have been reported.

Dangerous inflammation

Meningitis is an inflammation of the lining of the brain and spinal cord. The fungal form is unusual and cannot be spread from person to person, but can be extremely hard to treat.

The time from infection to onset of symptoms is estimated at anywhere from a few days to a month, so some people may not have fallen ill yet, health officials said.

The Minnesota Health Department sent an alert to all doctors, advising them how to treat any patients who do have infections. Antifungal drugs are being given, regardless of whether patients' symptoms are specifically traced to fungal infections, Lynfield said.

Meanwhile, in an alarming indication that the outbreak could grow bigger, Massachusetts health officials said the Framingham pharmacy has recalled three lots consisting of a total of 17,676 single-dose vials of the steroid.

An unknown number of those vials reached 75 clinics and other facilities in 23 states between July and September, federal health officials said. Several hundred of the vials have been returned unused, but many others were used. At one clinic in Evansville, Ind., more than 500 patients got shots from the suspect lots, officials said. At two clinics in Tennessee more than 900 patients, perhaps many more, did.

A common thread

The investigation began about two weeks ago, after a case of fungal meningitis was diagnosed in Tennessee.

Investigators said they are still trying to confirm the exact source of the infection, but the one common theme in all the illnesses is that each patient got the steroid medication.

Last week, New England Compounding issued a recall of three lots of the steroid. In a statement Wednesday, the company said it had voluntarily suspended operations and was working with regulators to identify the source of the infection.

Compounding pharmacies mix ingredients for customized medicines that generally aren't commercially available, are needed in different doses or formulations, or are in short supply. They are regulated by states.

This report includes information from the Associated Press. Jeremy Olson • 612-673-7744

TRACK THE OUTBREAK

To see an interactive map of the U.S. meningitis outbreak, go to startribune.com