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.
"It's 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.
Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, said it may bear similarities to polio, which smoldered among humans for centuries before it exploded into fearsome epidemics in the 19th and 20th centuries.
Fauci, who published a report about the disease Tuesday in the journal , said it is unlikely AFM will become as bad as polio, which struck tens of thousands of U.S. children annually before a vaccine became available in the 1950s.
But he warned: "Don't assume that it's going to stay at a couple of hundred cases every other year."
While other countries have reported cases, including Canada, France, Britain and Norway, the size and pattern of the U.S. outbreaks have been more pronounced. More than 550 Americans have been struck this decade. The oldest was 32. More than 90% were children, most around 4, 5 or 6 years old.
Most had a cold-like illness and fever, seemed to get over it, then descended into paralysis. In some cases, it started in small ways — for example, a thumb that suddenly wouldn't move. Some went on to lose the ability to eat or draw breath.
Many families say their children have regained at least some movement in affected limbs, but stories of complete recovery are unusual. Health officials cannot say how many recovered completely, partly or not at all, or how many have died, though the Centers for Disease Control and Prevention says deaths are rare.
Scientists suspect the illness is being caused chiefly by a certain virus that was identified more than 55 years ago and may have mutated to become more dangerous. But they have yet to prove that.
And while doctors have deployed a number of treatments singly or in combination — steroids, antiviral medications, antibiotics, a blood-cleansing process — the CDC says there is no clear evidence they work.
Many parents say that when they first brought their child to the emergency room, they quickly realized to their horror that the doctors were at sea, too.
"Everyone is desperate for some magical thing," said Rachel Scott, a Tomball, Texas, woman whose son Braden developed AFM in 2016 and has recovered somewhat after intensive physical therapy but still cannot move his right arm and has trouble swallowing and moving his neck.
A growing number of experts agree that physical therapy makes a difference.
"These kids can continue to recover very slowly, year over year. ... It's driven by how much therapy they do," said Dr. Benjamin Greenberg of UT Southwestern Medical Center in Dallas, one of the nation's foremost experts on the condition.
Wilcox, Joey's father, said his son made huge improvements that way. Joey can run and use his arms. Still, muscle tone is weak in his right leg and shoulder, and he still has left-side facial paralysis. "He can't completely smile," his dad said.
Other stories are more tragic.
Katie Bustamante's son Alex developed AFM in 2016. The suburban Sacramento, California, mother realized something was wrong when she asked the boy, then 5, why he wasn't eating his yogurt. Alex replied that his thumb had stopped working and he couldn't hold his spoon.
That morning was the start of 17 months of hospital stays, surgeries, therapy, and struggles with doctors and insurers to find a way to restore his ability to breathe. It ended one morning last May, when Alex died of complications.
Government officials need to step up, Bustamante said.
"I want them to research it and find the cause, and I want them to find a way to prevent it," she said. "This is growing. This shouldn't be happening."