Some patients who received a tainted steroid injection from a Framingham specialty pharmacy are now dealing with a second illness, beyond the fungal meningitis.

Some patients are also developing an epidural abscess, which is a collection of pus between the outer covering of the brain and spinal cord and the bones of the skull or spine, reports CNN.

These abscesses have formed even while patients were taking powerful antifungal medicines, putting them back in the hospital for more treatment, often with surgery.

"This is not typical for fungal disease," Dr. Tom Chiller, who serves as deputy chief of the CDC's Mycotic (fungal) Diseases Branch told CNN. While he and other health officials have been hearing about epidural abscesses since the beginning of the outbreak, it is unclear how many patients have had the abscesses.

“We don’t really understand the natural history of this disease. ... This is really new territory that is being explored,” CDC spokesman Curtis Allen said of the new menace, emerging just as the number of new meningitis cases was “going down.”

Since it was first identified that patients who received a steroid injection linked to New England Compounding Center in Framingham were contracting fungal meninitis, 37 people have died and more than 590 have been infected. (None of the cases are in Massachusetts, but an Andover woman may be the first case related to the deadly fungal outbreak.)

The CDC said it has received 39 cases attributed to paraspinal abscesses, recently.

The main symptom is severe pain near the injection site. But the abscesses are internal, with no visible signs on the skin, so it takes an M.R.I. scan to make the diagnosis. Some patients have more than one abscess. In some cases, the infection can be drained or cleaned out by a neurosurgeon.

But sometimes fungal strands and abnormal tissue are wrapped around nerves and cannot be surgically removed, said Dr. Carol A. Kauffman, an expert on fungal diseases at the University of Michigan to the New York Times. In such cases, all doctors can do is give a combination of antifungal drugs and hope for the best. They have very little experience with this type of infection.

If left untreated, the abscesses can lead to permanent nerve damage, bladder and bowel dysfunction, as well as meningitis, according to Dr. William Schaffner, chairman of the Department of Preventive Medicine at Vanderbilt University in Nashville.

“They can be a stringy, tenacious mess,” Schaffner said. “These abscesses could continue to smolder and eventually work their way through the dura, the membrane that surrounds the spine.”

Federal health officials estimated as many as 13,000 patients in 23 states received the injections, but it is unclear how many more could still develop infections.

“One of the big questions is what is the incubation period?” said Boston University epidemiologist Dr. David Ozonoff told the Boston Herald. “We really don’t have a lot of data on this, so we are getting it the hard way.”

Most important, if anyone received an injections from the three tainted lots of the preservative-free steroid methylprednisolone acetate distributed by NECC, they need to see their doctor with any new symptoms or concerns.

NECC recalled every product in made back in October.

Last week, federal health officials released a report which identified products beyond the original steroids, that contained fungi and bacteria.

Besides fungal meningitis, patient have reported contracting arachnoiditis and other infections, too.

A raid of NECC by health officials discovered mold and other unsanitary conditions.

More than 70 lawsuits have been filed since the deadly outbreak began in October. Recently, a grand jury began investigation New England Compound Center, its owners and its employees for a criminal suit.

Recently, a federal judge has ruled any criminal case against a Framingham specialty pharmacy New England Compounding Center (NECC) would have priority over the numerous civil suits.

In November, two congressional hearings and one hearing at the Massachusetts statehouse was held on how this deadly outbreak could have happened.

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Click here to find all of Framingham Patch’s coverage of NECC and the meningitis outbreak.