Last year, health officials confronted a record number of cases of a rare, mysterious neurological condition that caused limb weakness and paralysis in more than 200 children across the country.

Officials with the Centers for Disease Control and Prevention said on Tuesday that they were still trying to understand the condition, called acute flaccid myelitis, or A.F.M. And though there have been very few cases so far this year, they urged doctors to be on the lookout because the illness has tended to emerge in late summer and early fall.

A.F.M. often involves sudden muscle weakness in the legs or arms and can also include stiffness in the neck, drooping eyelids or face muscles, problems swallowing and slurred speech. The paralysis can appear similar to polio.

There have been 570 recorded cases since 2014, when the C.D.C. began tracking the condition, and it appears to peak every two years from August through October. In 2018, there were 233 cases in 41 states, the largest reported outbreak so far, the agency reported Tuesday.