Doctors say a mysterious illness sticking children is not polio, but mirrors many of the symptoms.
As many as 20 children in California have suffered paralyzed arms and legs because of the disease.
Two neurologists stood before reporters at Lucile Packard Children's Hospital Monday evening, and admitted what they do know about the malady isn't good.
"All of the children have permanent weakness in the most severely affected limbs," explained Dr. Keith Van Haren, a pediatric neurologist at Stanford.
He and other specialists want to spread the word about the disease, not to alarm families, but to make them and doctors aware it exists. At this time doctors say the disease is not treatable.
Doctor Van Haren was joined by one of his patients, four year old Sofia Jarvis, a bouncy redhead who squirmed in her parent's arms.
"Sofia is still a healthy young girl who's thriving," said her mother, Jessica Tomei. "She goes to preschool and dance."
But one of Sofia's arms hangs limp, paralyzed.
"We call her left arm 'lefty'," added Tomei, "in order to make sure it's still part of her body, and she goes to physical therapy to keep it healthy."
The Berkeley family has two sons, ages 7 and 9, who are healthy and so was Sofia, until the sudden ordeal that struck two years ago.
As her mom described it, Sofia was having trouble breathing and her pediatrician assumed the wheezing was asthma. But repeated trips to the doctor and hospital didn't make her any better, and inexplicably, she couldn't grasp a toy in her hand.
"Over three days, she wasn't using her left arm at all, and that was very worrisome,” recalled Tomei.
No one knew it then, but an apparent virus, extremely rare, had attacked Sofia's spinal cord.
"On a child the size of Sofia it's about the size of your pinkie finger," her father Jeff Jarvis, said. "And it's a delicate piece of machinery. When things happen to it, they happen fast."
Sofia is the youngest of five Bay Area children also stricken with the disease. The oldest is 17, and one of the victims has lost the use of all four limbs.
"It's serious if you're affected but the odds of being affected are extremely, extremely unlikely," reassured Dr. Van Haren.
There is no warning, although other children, like Sofia, suffered respiratory symptoms beforehand.
Those tracking the disease admit they don't know how it's spread and most discouragingly, there is no treatment, and the paralysis is permanent.
"This is extremely rare," Dr. Emmanuelle Waubant of UCSF told reporters.
Nevertheless, the Neurology professor had this advice for parents: "If you notice sudden onset of weakness in your child that persists for more than a few minutes we suggest you seek medical care urgently."
Similar outbreaks have occurred around the world, most notably Southeast Asia and Australia, often linked to a polio-like virus. But it's too infrequent in the U.S. to get a handle on.
"We need more cases to make sure what it is, that explains these findings," said Dr. Waubant.
By publicizing the illness, it is hoped other doctors may recognize and report additional cases. Most have never seen symptoms like this, since polio was eradicated decades ago.
For Sofia's family, and the others affected, it's uncharted medical territory. But her parents focus on what they have and not what she has lost.
"I know we are so lucky that she's here,” said her mother, emotionally. "I know that many families go through losing a child, so we're so grateful that Sofia is with us today."