West Nile virus (WNV) is the leading cause of mosquito-borne viral disease in the United States with over 39,000 cases since it was first recognized in the U.S. in 1999 through 2013.  Many different bird species in the United States harbor WNV, and the virus is transmitted from bird to bird by feeding mosquitoes.  Humans can become infected by the bite of an infected mosquito.

Average annual incidence of West Nile virus neuroinvasive disease reported to CDC by county, 1999-2013

Source: ArboNET, Arboviral Diseases Branch, Centers for Disease Control and Prevention

Outbreaks of WNV have occurred every year since 1999, but the number of cases and location of the outbreaks have varied significantly.  There is currently no vaccine or specific treatment for WNV so mosquito control or personal protective behaviors such as wearing long sleeves or mosquito repellant are the best methods for preventing disease. The ability to predict when and where outbreaks will occur would help allocate limited public health resources.

RAL is working collaboratively with the Division of Vector-Borne Diseases at the Centers for Disease Control and Prevention to develop a model to forecast human WNV outbreaks prior to the coming season.  RAL is providing our modeling expertise as well as climate and land use data that will be used to predict WNV cases.