Doesn’t mean it couldn’t be a new and improved version from some third world Petri dish.
In her case she let herself get very physically run down. This allowed a previously undetected exposure or very mild case of Polio to come back on her and is such called Transverse Myelitis. It attack the Myelin. She was born in 1950 so there was a real good chance she was exposed. She also had taken the Polio vaccines as a kid. That means blood work for Polio would not tell anything.
The Polio aspect came into play when the Physical Therapist were doing limb measurements. There was very significant differences pointing to Polio at some point in her life but not notable as such just by a visual exam.
Basically she had an auto-immune attack due to getting run down. This was happening before we married and she wasn't eating good and was a single mom raising kids alone due to abandonment by husband. These could be illegal entry kids with weakened immune systems or possibly carriers of virus kids here have little immunity too. Many things are possible.