A mysterious polio-like illness has affected as many as 25 children in California. The illness causes paralysis in the limbs of the affected children, and since doctors don't know what's causing it, there's little hope of recovery. 

The patients suffer rapid-onset weakness or paralysis and their spinal cords show damage similar to that found in people with polio.  

A doctor at Stanford University's Lucile Packard Children's Hospital is presenting five cases of the mysterious illness at the American Academy of Neurology's meeting this year.  

All the afflicted children have been vaccinated against polio, which has been eradicated in the U.S.  

The first known case of the mystery illness was back in 2012, when 2-year-old Sofia Jarvis of Berkeley began having trouble breathing. The young girl spent a few days in the hospital -- doctors thought she was suffering from asthma. 

But on a follow-up visit, the young girl's mother noticed something else wrong. Sofia went to grab something with her left arm, and then stopped halfway. There was a noticeable weakness, in her arm. It was eventually determined to be paralysis.

Sofia was treated with steroids and intravenous immunogloubin therapy, in an attempt to reduce the severity of infections. None of it helped. Doctors informed the girl's parents that there was little chance of recovery. 

Doctors and medical professionals are telling parents not to panic, this is still very rare. However, they are asking that if parents notice any sudden onset of weakness to contact a medical professional immediately.

California is working with the Centers for Disease Control and Prevention in Atlanta to see if any cases outside of California have been reported. So far, none have. 

Children who suffer from this mystery illness do not have polio. But the symptoms are almost identical to those of the disease that terrified generations of parents beginning in the late 19th century. 

Kids who suffer from the disease lose the ability to lose one or all of their limbs, which then just dangle from the body. Since they can't be moved, they begin to lose muscle and start to atrophy. 

Polio is a highly infectious disease caused by the polio virus. It invades the nervous system and in one in 200 cases causes irreversible paralysis, according to the World Health Organization. It was not until the introduction of the Salk vaccine in 1954 that any protection against it was available.

So if it's not polio, what is it? 

Well, doctors aren't exactly sure. Some believe it may be an enterovirus. An enterovirus is a family of viruses that includes polio and hand, foot and mouth disease -- which is fairly common in infants. 

While there is a vaccine for polio, there aren't any for the other enteroviruses. 

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