There have been a few posts about Enterovirus D68 - virus associated with polio-like symptoms in children. Some have suggested it is related to polio vaccine or other vaccines. It is true that vaccines need to be addressed - ways to improve/support the immune system without them if that is the wish, but this post is about:

Enterovirus D68.

The polio-like symptoms are associated with a "new" clade = strain of Enterovirus D68.

"In June and July 2016, we identified 8 adults and 17 children with respiratory enterovirus D68 infections. Thirteen children required intensive care unit admission because of respiratory insufficiency, and 1 had concomitant acute flaccid myelitis. Phylogenetic analysis showed that all of 20 sequences obtained belong to the recently described clade B3."

https://wwwnc.cdc.gov/eid/article/23/1/16-1313_article

Another study identified "Genetic changes found in a distinct clade of Enterovirus D68 associated with paralysis…isolates carry the same residues observed at equivalent positions in paralysis-causing enteroviruses"

https://www.ncbi.nlm.nih.gov/pubmed/28512577

So it appears Enterovirus D68 has genetic material similar/identical to that found in true polio virus and this change is the cause of the "new" outbreak. Whether the change occurred by a "natural selection process" or during genetic manipulation /research is unknown and has not been discussed as far as I know.