Possibly. When the Physical Therapist checked my wife's limb measurements a few months after onset they said her limbs were typical for Polio at some point in her life. We think a mild undetected case that wasn't detected but did neurological damage. "IF" the poor kid has at some point came in contact with Polio that went undetected it might explain it.
BTW Transverse Myelitis itself IS NOT Contagious.
Scary. I had a mild case of Polio as a child back in 1956 and it went undetected for a year.