mosquitoes of the Culex pipiens species are of particular concern
Check with the CDC to see the most current areas are found.See below for the most current numbers:http://diseasemaps.usgs.gov/wnv_us_human.html
for horses, yes for people, no
Its all of them
viruses don't have legs (or heads, or eyes, etc) they're one-celled, like bacteria, only smaller in fact, they're more like "half a cell" since they don't have a lot of the elements in a standard...