A number of California children have been stricken with a "polio-like disease."

"Although poliovirus has been eradicated from most of the globe, other viruses can also injure the spine, leading to a polio-like syndrome," case report author Keith Van Haren, MD, with Stanford University in Palo Alto, Calif., and a member of the American Academy of Neurology and co-author Emanuelle Waubant, MD, University of California-San Francisco, said in a news release. "In the past decade, newly identified strains of enterovirus have been linked to polio-like outbreaks among children in Asia and Australia. These five new cases highlight the possibility of an emerging infectious polio-like syndrome in California."

A polio (a contagious disease that can cause paralysis) epidemic hit the U.S. in the 1950s, but a vaccine helped wipe out the disease. Today polio has been almost completely eradicated from the globe; but other diseases can still harm the spine.

Researchers looked at polio-like infections in children who had participated in California's Neurologic and Surveillance Testing program. The team looked at children who had paralysis in at least one limb and an abnormal MRI scan of the spinal cord. Children suffering from Guillain-Barré syndrome and botulism were not included in the study.

The five children believed to have a polio-like illness all had experienced sudden paralysis in a limb and was most sever two days after the condition's onset. Three had experienced a respiratory illness before the other symptoms appeared. All five children had received a polio vaccine.

After six months of treatment the children's symptoms had not improved. Two of the children tested positive for enterovirus-68 (a rare polio-like disease) while the cause of the other three children's conditions is still unknown.

"Our findings have important implications for disease surveillance, testing and treatment," Van Haren said. "We would like to stress that this syndrome appears to be very, very rare. Any time a parent sees symptoms of paralysis in a child, the child should be seen by a doctor right away."

Update: The number of cases being investigated for the polio-like illness is up to 25 according to CBS News.