Palo Alto, Ca. -- A medical mystery is surfacing in Oregon's neighboring state, California.
At least five children are suffering from a polio-like illness and there could be many more.
The afflicted kids are suffering from severe weakness or paralysis.
NBC 5 News spoke with a local doctor to find out if Oregon families should be concerned and what can be done to families.
It's only when four-year-old Sofia Jarvis walks that you can tell
something is wrong with her left arm. She's paralyzed from a polio-like condition.
"Sophia went to the treasure box to grab her toy after seeing the doctor, and I saw her left-hand mid-grasp stop working," said Jessica Tomei, the girl's mother.
Sofia is one of five confirmed cases of a mystery illness 20 more are suspected.
The cases are all in California. Doctors in Oregon said because there's no known link between patients, not to be concerned just yet.
"We don't really know exactly what's going on and it doesn't look like these cases are connected so parents shouldn't be going crazy over this," said Dr. Robin Miller, a general internist who also appears on NBC 5 News as a medical expert.
The illness can start with cold or flu-like symptoms and paralyzes at least one limb.
The current cases sound similar to polio, but are not. Polio was eradicated in the United States decades ago with a vaccine.
"I don't think people realize what Polio did because it's been so long since anyone's been inflicted but it can come back," said Miller.
Doctors suspect a virus is to blame and say that while frightening, they want to reassure parents the condition is very uncommon.
"This is extremely rare. But in the event that you ever notice a weakness in your child that persists for more than few minutes we always would advise you to seek medical care urgently," said Dr. Keith Van Haren who practices at Lucile Packard Children's Hospital in Palo Alto, California.
Sofia's illness began two years ago with wheezing. Paralysis set in within a week.
"It was scary when I got my IV," said the little girl.
Sofia is undergoing physical therapy, but so far no treatments have helped.
Doctors are encouraging their colleagues nationwide to watch out for similar cases.
Reported cases of the mystery illness have been confined to California. If they appear in other states, the Centers for Disease Control and Prevention will step in to help investigate.