Fewer cases are popping up of the Enterovirus-D68 (EV-D68), a cousin to the common cold that first appeared in August and causes wheezing in children. “Enteroviruses taper down as the weather gets cooler,” says Teri Schreiner, pediatric neurologist at Children’s Hospital Colorado.

A new twist appeared when kids started having muscle weakness related to the virus. From August 1 until October 20, there were 37 cases nationwide of muscle weakness with a preceding respiratory illness. Fourteen of those were in Colorado and 13 treated at Children’s Colorado.

The weakness sometimes referred to as “paresis” or “paralysis-like” can affect the arms, legs, face, eye muscles or throat.

The worst muscle case was a child who had to be intubated because he could not breathe on his own. He can now walk but doesn’t have strength in his arm.

It’s unclear how the weakness is related to the virus. Five of the 13 cases at Children’s Colorado tested positive for EV-D68. Schreiner suspects more of the kids had the virus but came in weeks after their respiratory symptoms.

“We see kids improving but they’re not totally back to normal,” says Schreiner, who specializes in how the immune system affects the nervous system. The virus is not showing up in the cerebral spinal fluid or blood. MRIs show inflamed anterior horn cells, or the part of the spinal cord that controls motor nerves.

Schreiner is part of a task force coming up with guidelines for treatment for the Centers for Disease Control. Medicine has shown little effectiveness and time has proven the best treatment. Some kids have come in with mild conditions. Most kids take at least a month to start recovering. Three patients are still in the hospital and 10 have been discharged. Two to three months after being released they will come back into the clinic for a checkup.

There is no way of knowing whether there is any permanent neurological damage from the weakness. Schreiner hopes with the fewer cases of EV-D68 they will see fewer kids with muscle weakness.