An emerging disease in California, which presents with Polio-like symptoms, has left doctors alarmed. The disease may have infected up to 20 children, all of whom were previously healthy but showed signs of the disease from as early as 2012.

The American Academy of Neurology suggested in a statement that the illness may be caused by an infectious virus. The statement highlighted research from two neurologists in California.

Although polio is not an issue in the United States, similar viruses can attack the body’s nervous system and lead to similar symptoms, such as paralysis. Some of the patients who had been infected with this polio-like virus became paralyzed in all four limbs, and have not yet show signs of improvement with treatment.

Despite concerns that have been raised over this new illness, doctors state that they do not expect it to become an epidemic. Additionally, they stress that this infection is still quite rare.

Over the course of the last 18 months, around 20 new cases have been suspected. Five of the cases were found to be possibly linked to enterovirus-68, which is related to poliovirus. The children had received polio vaccines.

Enterovirus is what causes a summer cold, and it reaches its peak in the months of July, August, and September. Children and teens are more likely to become ill, as they have not yet built up immunity.

This infection is usually mild and resolves on its own, although certain types are more serious. Examples include viral meningitis, hand, foot, and mouth disease, heart infection, inflammation of the brain, and paralysis in some cases.

These cases cover an area of around 100 miles in diameter, making it less likely that the illnesses stem from a single cluster or outbreak. However, researchers note that as was the case with polio, it is possible that a much higher number of people were infected, but never developed serious symptoms.

Dr. Keith Van Haren of Standford University, a researcher on the case, explained that although the illnesses might represent an emerging, infectious disease similar to polio, it still seems to be quite rare. He concludes, “Any time a parent sees symptoms of paralysis in a child, the child soon be seen by a doctor right away.”