A mysterious illness that mimics the worst symptoms of polio has infected as many as 25 children in California since 2012, leaving them with paralyzed limbs, doctors say.
The infections, possibly caused by a virus, are still very rare and there’s no widespread cause for alarm. But researchers say they’re concerned about the problem detected in kids ages 2 to 16, including up to 20 new cases since last summer.
"We're seeing them throughout California," said Dr. Keith Van Haren, a pediatric neurologist at Stanford University's Lucile Packard Children's Hospital. "The farthest north is in the Bay Area and the farthest south is in San Diego."
In all of the cases, the children developed sudden weakness in their limbs that couldn't be explained by more common causes, such as Guillain-Barre syndrome or botulism poisoning. They all had been vaccinated against polio.
Van Haren and his colleagues have been working with the California Department of Public Health to track the illnesses. At first, there were just one or two cases, but when it became clear there may be more, the scientists decided to review a large database, California’s Neurologic and Surveillance Testing program, to see if there was a wider problem. They found initial reports of five children, all in the larger San Francisco Bay Area, who had unexplained paralysis between August 2012 and July 2013.
Two of the children tested positive for human enterovirus-68, which previously had been associated with polio-like symptoms, but three did not. HEV-68 is a rare form of very common enteroviruses, which cause between 10 million and 15 million infections in the U.S. every year, according to the Centers for Disease Control and Prevention. Like polio infections, most enterovirus cases cause no symptoms or only mild illness, but a fraction of cases can turn terribly serious.
Polio infections once paralyzed up to 20,000 people a year in the U.S., mostly children, until a vaccine eradicated the disease in the U.S. and nearly eradicated it worldwide.
Similar enterovirus outbreaks have caused polio-like symptoms in children in Asia and Australia, the researchers said.
The chance of infection remains very rare, Van Haren said. He urged parents of children with unexplained limb weakness to contact their doctors. Health officials in California will continue to track the problem, he added.
"It does represent a rather distinct increase in what we've seen historically," he said. "This is something different."