One morning last fall, 4-year-old Joey Wilcox woke up with the left side of his face drooping.

It was the first sign of an unfolding nightmare.

Three days later, Joey was in a hospital intensive care unit, unable to move his arms or legs or sit up. Spinal taps and other tests failed to find a cause. Doctors worried he was about to lose the ability to breathe.

Its devastating, said his father, Jeremy Wilcox, of Herndon, Virginia. Your healthy child can catch a cold and then become paralyzed.

Joey, who survived but still suffers some of the effects, was one of 228 confirmed victims in the U.S. last year of acute flaccid myelitis, or AFM, a rare, mysterious and sometimes deadly paralyzing illness that seems to ebb and flow on an every-other-year cycle and is beginning to alarm public health officials because it is striking more and more children.