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Communicable and Environmental Disease

West Nile Virus

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.

mosquitoWest 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).

Dead Bird Submission

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

Repellant Information

Detection of West Nile Virus in Tennessee by Year

Year Human Horses Birds Mosquito Pools
  Positive Positive Positive Positive
2000 0 0 0 0
2001 0 1 46 0
2002 56 141 823 307
2003 26 103 275 308
2004 14 15 34 405
2005 18 7 12 574
2006 22 8 1 626
2007 11 4 7 600
2008 19 6 3 658
2009 8 5 1 488
2010 4 3 0 403
2011 18 3 0 995
2012 33 6 6 916
2013* 0 0 0 0

*As of 04/17/2014

 

Number of Human WNV Cases and Deaths by Year

For more detailed information: See the complete report by county

U.S. Geological Survey West Nile Virus Maps 2006 and Previous Years

Shows WNV activity in mosquitoes, birds, horses and humans in the United States.   Please note that this data may be one to two weeks behind.