West Nile; How serious is it?

West Nile Virus is claiming more and more lives each year. This virus is new to the United States but it has been around the Middle East for as long as we can find recorded history. Generally West Nile Virus is delivered to us humans via the mosquitoes. A species which has been giving it to us since 6000 B.C. and was very prevalent around 2700 B.C.. Additionally we have found writings dating back that far which tell of another virus causing many to die during one of the Earth