Public Health Advisory: West Nile Virus Published Aug. 25, 2015 28th Medical Group Public Health ELLSWORTH AIR FORCE BASE, S.D. -- The 28th Medical Group Public Health office has released an updated Public Health Advisory regarding West Nile Virus. The South Dakota Department of Health has reported nine cases of the West Nile Virus disease since May 2015. The disease is spread by mosquitoes, and the 28th Medical Group Public Health office is responsible for trapping and testing mosquitoes, with positive test results in 2013 for both West Nile and Saint Louis Encephalitis. In 2014 and more recently, mosquito tests on base indicated positive for West Nile. The risk of becoming infected with the West Nile Virus can be reduced by using mosquito repellent containing DEET, Picaridin or oil of lemon eucalyptus, and minimizing time spent outdoors between dusk and dawn. The full advisory may be found by clicking here. For more information, visit the Centers for Disease Control or contact the 28th MDG Public Health office at (605) 385-3383.