MINNEAPOLIS - Halloween is a welcome treat for Dr. Mark Schleiss. When he's not at home, this professor of pediatrics at the University of Minnesota Medical School often sees kids when they're not so healthy and recently there's one topic that keeps spooking their parents.

For several weeks, concern has been mounting locally and nationally about an outbreak of a virus that can cause weakness and paralysis in the arms and legs of children. It's known as AFM, which is short for Acute Flaccid Myelitis.

"Acute means it comes on suddenly," said Dr. Mark Schleiss, a professor of pediatrics at the University of Minnesota Medical School.

"Flaccid means you lose control, usually of an arm, or sometimes all extremities in severe cases. Myelitis just simply means infection of the spinal cord, so that does sound scary," said Dr. Schleiss.

The Minnesota Department of Health has confirmed seven cases of AFM in the state since September and, according to the CDC, there have been a total of 72 confirmed cases in 24 states this year.

But Dr. Schleiss says what's been billed as a mystery illness, isn't quite as mysterious as it seems.

"Anyone who works in a children's hospital setting is familiar with AFM," Schleiss said. "We typically get one or two cases a year, and even though we've seen this uptick in 2018, it comes on the heels of an uptick that's really been going on for a while."

The CDC documented similar spikes in AFM cases in 2014 (120 cases) and 2016 (149 cases). In each of those years, including 2018, the vast majority of cases were reported in September.

Still, the CDC is searching for a common link that will point to what is causing it.

"By the time a child has paralysis from AFM, the infection has already kind of run its course," Schleiss said. "So it's hard to find the virus."

But that's not stopping medical professionals from teaming up to find out more. The U of M Masonic Children's hospital is now collaborating with Children's Hospitals of Minnesota, the Minnesota Department of Health and the CDC to communicate information about their cases. They're also beginning to communicate with researchers across the country to develop a plan forward, in hopes of making the future a little less scary.

"A network is emerging of interested and concerned investigators who want to work together to try to understand this outbreak better," Dr. Schleiss said. "Trying to establish a network to test hypothesis about why we've seen this uptick all over the country this year."