WNV has affected 1118 Humans and 114 Equine this year as reported by the USGS through August 21, 2012. The threat is real and transmitted by mosquitoes that have picked up the virus from birds. Please vaccinate your horses and take preventative measures to protect yourself. For more information:
http://diseasemaps.usgs.gov/wnv_us_human.html
http://www.allabouthorses.com/west-nile-virus/