Dr. Kevin Messacar, left, Dr. Sarah Pilarowski, right, and Lydia Pilarowski, 9.

(Hart Van Denburg/CPR News)

Lydia Pilarowski, who is 9 years old now, came down with a polio-like illness in 2014 — one of many kids to contract what the news media called a mystery illness, with an epicenter in Colorado. For this little girl, symptoms started with a fever, then a cough, followed by a weakness in her arms. She and her mother, Sarah Pilarowski, who’s also a pediatrician, tell Colorado Matters about experiencing the illness.

Now, University of Colorado researchers along with colleagues around the world, say they've identified the likely cause. Acute flaccid myelitis is a neurological illness that can cause paralysis, facial drooping and muscle weakness. In 2014 there were more than 100 cases in 34 states, including 12 cases treated at Children’s Hospital Colorado. Another wave of cases appeared in 2016.

The CDC reports that far fewer cases (23) were reported nationally in 2017. Dr. Kevin Messacar with Children's Hospital Colorado said "we haven't had any cases" in Colorado in 2018, so far.

All of the Colorado children with the disease eventually got better, but most still have some residual weakness in their arms and legs. “As a scientific community we need to take it seriously because of the long-term consequences and potentially disabling consequences of it,” Messacar said.

Editor's Note: The original version of the story misstated numbers attributed to the CDC on recent cases of acute flaccid myelitis. The count for 2017 has been corrected and 2018 numbers are not yet available. We regret the error.