Department of Health
John J. Dreyzehner, MD, MPH, Commissioner

West Nile virus (WNV) is one of several mosquito-borne viruses in the United States that can infect people. The virus exists in nature primarily through a transmission cycle involving certain species of mosquitoes and birds. Mosquitoes become infected with WNV when they feed on WNV infected birds.

West Nile virus has emerged in the 1990s in temperate regions of Europe and North America and was introduced into New York City in 1999. The virus has moved westward from New York to California and in 2003 was documented in 46 states.

Most people (about 80 percent) that are infected with WNV by the bite of an infected mosquito will have no symptoms and will not know they have been infected. Approximately 20 percent of the people that are infected may experience a range of flu-like symptoms which may include fever, headache, weakness, stiff neck, nausea, vomiting, muscle aches and pains, rash and in some cases diarrhea and sore throat. Less than 1 percent of people that are infected with WNV by the bite of an infected mosquito will develop severe illness. Persons over 50 years of age are at highest risk of developing the most severe form of the disease and persons over the age of 70 with other health problems are at greatest risk for death.

As with any disease, the public should respond appropriately with increased awareness of WNV and focus on personal preventive measures. Individuals can significantly reduce their chances of acquiring West Nile virus by taking very basic precautions which include personal protective measures such as wearing insect repellents when in mosquito habitats and wearing long pants and sleeves that will provide a physical barrier against mosquito bites. Since immature mosquitoes require stagnant water for development, inspect your yard and neighborhood for any stagnant water that may collect in a variety of containers from bottle caps to abandoned swimming pools. Eliminate unwanted containers (tires, trash) or turn containers over as to not collect water (wheelbarrows, kiddie pools) and properly maintain wanted water sources such as bird baths, ornamental ponds).

To submit dead crows or blue jays for West Nile Virus testing, contact your local health department.

• Active Ingredients found in Insect Repellents from the U.S. Environmental Protection Agency
• I'm One Program: Mosquito Control to Protect Public Health from the American Mosquito Control Association
• West Nile Virus: Insect Repellent Use and Safety

*As of 05/23/2013

For more detailed information: See the complete report by county