Go here
http://www.enterstageright.com/archive/articles/0503/0503westnile.htm/ to read an interesting article on why the county waits and sprays for the adult mosquitoes instead of going after them in the larva stage...
Quote from the article…
“From May 5 to May 7, more than a hundred AMCA mosquito control experts met in Washington, DC, to urge members of Congress to let them do their job by easing restrictions on larvicide spraying. The problem is the Clean Water Act whose intent is to reduce pollutants. … According to Joseph M. Conlon, a spokesman for AMCA, instead of helping mosquito control authorities to protect human life, the restrictions would have "the perverse effect of increasing reliance upon adulticides to address mosquito populations historically controlled more effectively and safely using proven public health larvicides." … Simply stated, it's better to kill mosquitoes in their larva stage of development than to have trucks spraying pesticides to knock down the adult population. The object is to kill mosquitoes before they become a threat to the health of humans and other species.
Here again we see how the environmentally inspired Clean Water Act is having the opposite affect of "protecting" people. The EPA has stripped Americans of many of the pesticides that formerly protected them against a vast range of insect pests that spread disease or inflict millions of dollars of property damage. “
WNV first showed up in NY - I believe in the Long Island area - in 1999. Is it known how it was transported?