Powers would give a nation a lot of extra power to stand in the world. Since there will be government personnel (police, bureaucrats) who might also have gained some powers. Maybe they even help keep up the quarantine.
Just don't make it a city in the US. If you want a city on that continent take Mexico, Canada or one of the south american countries. ;)
ok thanks will have to think about choosing a city neat idea with the some gov people helping the quarantine