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West Nile Virus

Image: West Nile Virus and Mosquito Monitoring

West Nile Virus & Mosquito Monitoring

West Nile Virus (WNV) was first identified in Dane County in 2001, in a dead crow. Multiple WNV positive birds have been found in Dane County every year since then. For this reason, the emergence of the mosquito-borne West Nile Virus (WNV) in Wisconsin, and specifically in Dane County, has created the need for a public health response. The following is information about WNV, the illness that may result, and the PHMDC's response.

Go to state-wide and national public health information on West Nile Virus.

WHAT IS WNV?

West Nile Virus is a virus that was first identified in Uganda in 1937. This virus was first identified in the United States in 1999 during an outbreak in New York. Since that time, the virus has been found in mosquitoes, birds, horses, and humans throughout the United States.

HOW CAN I BE EXPOSED TO WNV?

People may be exposed to WNV when an infected mosquito bites them. However, only a small percentage of mosquitoes are expected to carry the virus so the risk of being infected with WNV from any single mosquito bite is very small. For a mosquito to become infected with the virus, it must bite an infected bird.

DO ALL MOSQUITOES CARRY WNV?

No. Monitoring data in the United States have indicated that mosquitoes in the Culex group are most often infected with WNV. This is significant because most of the nuisance mosquitoes in Madison belong to the Aedes group, which are less likely to carry the West Nile Virus. Culex mosquitoes found in the Madison area (usually Culex pipens or Culex restuans) are considered to be evening and nighttime biters and commonly breed in stagnant or polluted water.

CAN WNV MAKE ME SICK?

Most of the time, people infected with WNV will have no symptoms or will develop a mild illness that includes fever. In severe cases, encephalitis may develop. The Centers for Disease Control and Prevention (CDC) reports that less than 1% of persons that get infected will develop severe illness. Serious illness resulting from WNV can happen at any age; however, most cases of serious illness have occurred in persons greater than 50 years of age
Key Contacts
Report a sick or dead crow or blue jay:
1-800-433-1610

West Nile Virus in Dane County or Mosquito Monitoring & Control:
(608) 266-4821 or
email Public Health