A molecular surface model of West Nile virus, a mosquito-borne illness prevalent in temperate and tropical climate zones. While it was first identified in East Africa, the virus has spread globally to Africa, Europe, the Middle East and the United States. While most cases of West Nile do not present any symptoms, severe cases can lead to fever, nausea, fatigue or muscle aches. The elderly or very young are also more susceptible to neurological symptoms such as West Nile encephalitis or meningitis. Since there is currently no vaccine available, preventative measures such as using mosquito repellant or wearing long-sleeved shirts and long pants are used to reduce the risk of being bitten. Efforts are also made to control mosquito populations by removing areas of stagnant water that act as breeding grounds, as well as spraying pesticides.