West Nile Virus threat to human, animal health Published June 21, 2011 PETERSON AIR FORCE BASE, Colo. -- In recent years the West Nile Virus has emerged in areas of Europe and North America with somewhat moderate climates. This presents a threat to the public as well as animal health. According to the Colorado Department of Health, "The most serious manifestation of West Nile virus infection is fatal encephalitis (inflammation of the brain) in humans and horses, as well as mortality in certain domestic and wild birds." The WNV first appeared in North America in 1999 during an outbreak in New York City. There are currently four viruses, including the WNV, in Colorado that are transmitted by mosquitoes. Western equine encephalitis is distributed across the central and western United States. St. Louis encephalitis is found throughout the continental United States. California encephalitis viruses are a group of several viruses found throughout the United States. These viruses are transmitted to people and animals by bites from infected mosquitoes. The species of mosquito that is transmitting these viruses in Colorado feeds in the few hours around dawn and dusk. The virus is transmitted to a new host in the mosquito's saliva when the insect bites another person or animal. Person-to-person transmission does not occur. The virus is prevalent during the months of May to September when mosquitoes are most abundant but the risk to humans occurs primarily from August through early September. Most people that get infected with the virus do not become ill or have symptoms of the illness. For those who do become ill, symptoms include fever, headache and malaise. These symptoms persist for about two to seven days. The time between the bite and the onset of symptoms ranges from five to 15 days. In order to decrease the exposure to mosquitoes and the viruses they may carry, limit outdoor activity at dusk to dawn when mosquitoes are most active, wear protective clothing such as lightweight pants and long sleeve shirts when outside during these times, apply insect repellant to exposed skin when outside but use repellants with DEET sparingly especially for children (use products with 10 percent or less of DEET for children). Make sure that doors and windows have tight-fitting screens. Attempt to drain all standing water on your property no matter how small an amount. Make sure roof gutters drain properly and remove items that could collect water such as old tires, buckets, etc. For additional information contact Public Heath at 566-1225 or the El Paso County health department at 578-3199.