Cases of the polio-like illness Acute Flaccid Myelitis continue to rise, and officials aren't sure how it's spreading.

According to the Centers for Disease Control and Prevention, the agency is working hard to find the cause of the outbreak.

So far this year, 72 confirmed cases of the nervous system disease have popped up in almost two dozen states.

Some doctors around the country believe the CDC isn't doing enough.

"We feel that their potential is tremendous as an institution, The CDC is not rising to its potential in this particular case,” says Dr. Keith Van Haren, Assistant Professor of Neurology, Stanford Medicine. “We feel like they're not playing their A-game on this."

The disease is extremely rare, but usually affects children.

Symptoms include arm or leg weakness and difficulty swallowing.

Paralysis or death is possible in serious cases.