By Stephanie Stahl

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PHILADELPHIA (CBS) — More children have been diagnosed with a mysterious paralyzing illness in recent weeks, according to the Centers for Disease Control and Prevention.

The numbers continue to grow as the CDC says it has confirmed another two dozen cases of the illness that’s striking mostly children. While the disease is rare, there have been more cases this year than ever before.

It appears most patients with a polio-like condition called acute flaccid myelitis showed symptoms of viral infections before they developed the illness, according to the CDC.

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It says there are now 90 confirmed cases of AFM in 27 states and it is investigating an increasing number of potential cases. That number is up to 252.

AFM affects the nervous system, specifically part of the spinal cord. It causes weakness in the arms and legs, and in some cases, paralysis.

Some are accusing the CDC of underreporting deaths related to the illness and hiding information from the public.

“I’d hate to think that,” said Robin Roberts, whose 5-year-old son Carter died in September. “There would be another parent crying their eyes out because their child’s in an urn.”

Carter was diagnosed with AFM by three different medical centers, but the CDC says there have been no confirmed deaths from the illness.

“The reporting of the diseases has a lot of steps, so there may be a lag,” said Dr. Anne Schuchat, the CDC’s principal deputy director. “We are working 24/7 to increase recognition, to get the reporting into the system. Every one of these episodes is difficult and the deaths are really tragic.”

More than 400 people, mainly children, have been diagnosed with AFM since 2014.

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The CDC hasn’t been able to identify a specific virus that causes AFM. They also say it’s possible the illness is being caused by some new germ that hasn’t been identified, and they think in some patients, their immune systems react so severely, it causes paralysis.

The illness tends to spike in the fall every other year. It’s not known exactly why.

Stephanie Stahl