Its really interesting to dig into the Polio V[x]. The so called polio virus seems to have been caused by poisonous neurotoxins used in agriculture and amplified by the condition of the person. Eg a high sugar diet (COKE etc) weakend the spinal cord and made it susceptibe to polio. This was known way back but the soft drink industry was too powerful to challenge.
No virus was isolated in most "polio patients" etc.
Dr Suzanne Humphries writes well on this in her book.
If you dig and dig and dig you will get the nervous system, poison, sugar connections.
The polio V[x] was introduced to hide the real cause of polio and the removal of most of these poisons in farminng was the cause of its reduction, not the V[x]. The V[x] was a cover story.
