How Many Muscles were Affected by the Poliovirus?

A Bruno Byte “Tidbit” from
Richard L. Bruno, HD, PhD 
Director, International Centre for Polio Education

If the poliovirus got into your spinal cord, some motor neurons going to every muscle were damaged or killed. This was known in the 1940s and comes from Dr. David Bodian's research on monkeys and humans infected with polio. He found that 96% of motor neurons were damaged by the poliovirus but that at least 60% had to be killed before muscles show any weakness. So "unaffected limbs" and "non-paralytic" polio survivors could have lost 59% of their motor neurons and not have known since they had no muscle weakness!

This is why you can't "pump up" up your "good" leg or arm through exercise to compensate for muscle weakness on the other side of your body. It's also why polio survivors so often come in confused when that experience that their "good leg" is getting weaker even though they "didn't have polio" in that leg.

BOTTOM LINE: The poliovirus went everywhere!