There's no telling with journalists these days since few of them took science or math in school. The first part of the article leads you to think the stuff is able to somehow cause polio, and the headline too, but of course that's to be expected since hysteria sells newspapers. The latter part of the article implies more of a polio-like symptom associated with West Nile, which seems more plausible.
But what I was referring to was the possibility of deliberate manipulation of the genes by replacing part of the strand with a section from something else, and wondering if this could be done with WN and polio and if the results would be worth the effort for some scuzzball, or would they produce similar symptoms. Presumably the genome of both would have to be mapped out first, but I simply don't know.
Viruses causes different symptoms in different populations. West Nile is probably more severe in the U.S. because we haven't lived with it.
Now if you suspect the cases are due to deliberate introduction, I'm paranoid enough to listen to that. It wouldn't take much effort.