Authorities took the step to help identify everyone who may have gotten sick — or may still get sick — in the outbreak.
"All patients who may have received these medications need to be tracked down immediately," said Dr. Benjamin Park of the Centers for Disease Control and Prevention.
"It is possible that if patients with infection are identified soon and put on appropriate antifungal therapy, lives may be saved," he said in a statement.
The CDC said the number of cases of the rare fungal meningitis reached nearly 50 cases, and spread to a seventh state Friday. The number of deaths in the outbreak remained at five.
Investigators have focused on a steroid medication made by a specialty pharmacy in Massachusetts. All the outbreak patients had gotten shots of the steroid for back pain, a common treatment, and inspectors found at least one sealed vial contaminated with fungus.
On Friday, officials said they have found fungal infections in nine sick patients. They weren't able to identify what types of fungus in every one of those patients, but did distinguish at least two types — Aspergillus and Exserohilum.
In all, 47 people have contracted fungal meningitis, the CDC said. Michigan became the seventh state to report cases, with four. Tennessee's cases now total 29; Virginia, six; Indiana, 3; two each in Maryland and Florida and one in North Carolina.
Three people have died in Tennessee and one in Virginia and Maryland.
The first known case in the meningitis outbreak was diagnosed about two weeks ago in Tennessee, and the steroid was recalled last week by the pharmacy, New England Compounding Center in Framingham, Mass.
About 17,700 single-dose vials of the steroid were covered in the recall. On Friday, the government released the names of about 75 facilities in 23 states that got recalled doses between July and September.
It's not clear how many were sent to clinics, how many were used, or even whether everyone who got one will get sick. Once infected, it can take as long as a month for symptoms to appear.
At the prompting of government officials, clinics are notifying all the patients who got shots from the recalled lots.
"There's a massive effort to contact all the patients," said Marsha Thiel, the chief executive officer of MAPS, a company that owns surgery centre clinics in Minnesota.
She added, "If there's any question at all, they're being directed to go to their physician."
As a precaution, the Food and Drug Administration urged doctors not to use any of the company's products, and released a list Friday that included other steroids, anesthetics and a blood pressure medicine. The company, which is now closed, said in a statement Thursday that despite the FDA warning, "there is no indication of any potential issues with other products."
The steroid is known as preservative-free methylprednisolone acetate, which the compounding pharmacy creates by combining a powder with a liquid.
There are FDA-approved versions of the drug, sold by the brand name Depo-Medrol, in good supply. So patients who need the medicine should not encounter a shortage, the FDA said Friday.
Most of the anxiety now involves patients who got steroid shots for back pain and are worried about becoming seriously ill.
"Our phone is ringing off the hook this morning. Patients are calling. Of course, they're concerned," said Paulette Fry, practice manager at Wellspring Pain Solutions in Columbus, Ind., about 40 miles south of Indianapolis. She said the clinic was sending out letters to about 300 patients who received spinal injections with the drug.
Meningitis is an inflammation of the lining of the brain and spinal cord. Symptoms include severe headache, nausea, dizziness and fever.
Fungal meningitis is not contagious like the more common forms. The types of fungus linked to the outbreak are all around, but very rarely causes illness. Fungal meningitis is treated with high-dose antifungal medications, usually given intravenously in a hospital.
AP writers Charles Wilson in Indianapolis and Martiga Lohn in St. Paul, Minn., contributed to this report.
CDC list of facilities: http://www.cdc.gov/hai/outbreaks/meningitis-facilities-map.html
Recalled list: http://www.fda.gov/Drugs/DrugSafety/ucm322752.htm