Immaterial. The mosquitos borne of those eggs wouldn't be carriers of WNV...until they bit an infected bird or human.
Accordingly, the accidental introduction of a single mosquito, or just a few, would be insufficient to sustain and spread an outbreak. Presumably, a significant colony of infected mosquitos would be necessary to do that.
Recall, as well, where the first two outbreaks occurred: New York City and Washington, D.C.