Doctors in California warned on Monday that children showing signs of a rare, polio-like syndrome should immediately be seen by a doctor, after more than a dozen children in the state developed the syndrome over the past year.
The unusual illness is still being investigated, but within days it paralyzed one or more of the children's arms or legs, Stanford University researchers said.
"Sofia went to the treasure chest box to grab her toy," said the mother of Sofia Jarvis, one child who developed what looked like asthma two years ago. "And I saw her left hand mid-grasp stop working."
That was two years ago and has remained paralyzed ever since.
"The prognosis that we've seen so far is not good," said pediatric neurologist Dr Keith Van Haren at a news conference on Monday. "Most of the children we have seen have not recovered use of their arm or leg."
He said the syndrome resembles but is not the same as polio, and that doctors were not sure whether it is a virus or something else.
Noting similar outbreaks in Asia and Australia, he however stressed that so far it has remained extremely rare.
"We're reporting five cases," he said. "We appreciate the help in getting the word out to physicians and families but we want to emphasize that this is not a common phenomenon."
Van Haren, who diagnosed Sofia, said polio vaccines do not protect children from the disease, but he stressed that it is still important for children to receive that vaccine.
Officials at the United States' Center for Disease Control and Prevention have said that any of a number of illnesses could be at work, and it's possible some of the cases had one infection and some had another.
The California Department of Public Health has not identified any common causes that suggest the cases are linked.
University of California, San Francisco, neurology professor Emmanuelle Waubant said doctors believe, but don't have proof, that it's a virus that for most children shows up only as a benign cold.
She said a few children, due to their biological makeup, are having much more serious symptoms and she hoped doctors would look for them.
"By the time the weakness brings parents to the emergency room or to the attention to their pediatrician or their child neurologist, there may already be a fair amount of damage," she said.
However for Sofia, her parents are glad Sofia is up and about.
"I know that we're so lucky that she's here and I know that many families go through losing a child," her mother said on Monday. "We're so grateful that Sofia's with us today and she's going to do amazing things."
AP