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Fight the Bite SloganWest Nile virus

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West Nile virus (WNV) is an arbovirus that is transmitted by a bite of an infected mosquito. West Nile virus (WNV), which has been widespread in Africa, southern Europe, the Middle East and western Asia, first appeared in the New York City area of the United States in 1999. The first human cases of WNV in Wisconsin appeared in 2002. Few mosquitoes actually carry the virus.

An estimated 80% of people infected by WNV never experience symptoms. Most of the remaining 20% will experience relatively mild illness, with symptoms such as fever, headache, muscle pains, a skin rash, swollen lymph nodes, and photophobia. Less than one percent (approximately one of every 150 people) infected with WNV become seriously ill. Severe symptoms include a sudden onset of a high fever, neck stiffness, extreme muscle weakness, tremors, convulsions, or disorientation.

In nature, mosquitoes become infected with WNV by feeding on infected birds and can transmit the virus to other animals, birds, and humans. The Wisconsin Division of Public Health monitors dead birds for WNV as an early warning system to indicate that the virus may be present in an area. This information is important to heighten awareness in the prevention and control of WNV disease. People can report dead birds found near their homes to the following hotline:

Dead Bird Reporting Hotline 800-433-1610

Arboviral diseases home

General Information

West Nile virus fact sheet (PDF, 139 KB)  Spanish (PDF, 21 KB)  


Some tips to protect yourself:

  • Use effective mosquito repellant and apply according to the label instructions.
  • Wear long-sleeved shirts, long pants, socks, and shoes.
  • Mosquitoes may bite through thin clothing, so spraying clothes with a repellent containing permethrin or DEET will give extra protection. These repellants are the most effective and most studied.
  • Avoid being outside during times of high mosquito activity, specifically around dawn and dusk.
  • Keep window screens repaired so that mosquitoes cannot enter your home.
  • Dispose of discarded tires, cans, or plastic containers left outside that may contain standing water.
  • Drain standing water from pool or hot tub covers.
  • Turn over plastic wading pools and wheel barrows when not in use.
  • Change the water in bird baths, pet dishes and wading pools every 3-4 days.
  • Keep drains, ditches and culverts clean of trash and weeds so water will drain properly.
  • Clean gutters to ensure they drain properly.

For more information, Using Insect Repellants Safely - CDC

Data and Statistics 

2014 Annual Wisconsin Summary Data

Positive WNV Cases - Updated October 30, 2014

Avian (bird) 26
Equine (horse) 2
Mosquito pools 3
Human confirmed 5
Human probable ⃰  2
Deaths  ⃰  ⃰  1
Hospitalizations 5
Counties reporting WNV activity 30
 ⃰⃰  Probable cases have presumptive positive laboratory results without confirmatory testing at CDC.
 ⃰⃰  ⃰⃰  The deaths are included among the confirmed and probable cases.

Information for health professionals

This is a Wisconsin disease surveillance category II disease: 
Report to the patient's local public health department electronically, through the Wisconsin Electronic Disease Surveillance System (WEDSS), by mail or fax using an Acute and Communicable Disease case report F-44151 or by other means within 72 hours upon recognition of a case.
Information on communicable disease reporting

Wisconsin case reporting and public health follow-up guidelines Arboviral diseases EpiNet 
Arbovirus case report form
2014 Arbovirus management protocol  

WNV Clinical characteristics - CDC 
Risk Factors for WNV infections - CDC  

Laboratory guidance 

Training and additional resources 

Educational material available from the Department of Health Services:


Form Name
   DPH-42166 Use Protection, Avoid Infection” Mosquito-borne Pocket Card
West Nile Virus is Something You Can Do Something About with a Few Simple Steps, English
West Nile Virus is Something You Can Do Something About with a Few Simple Steps, Spanish
West Nile Virus and Transplant Recipients
Electronically order forms:
Follow the instructions at the top of the page and email the form F-80025A (can be used to order multiple forms/publications) to
Questions concerning ordering of forms can be addressed to Cris Caputo, 608-267-9054

Diep Hoang Johnson Vectorborne Disease Epidemiologist
Wisconsin Division of Public Health 
Bureau of Communicable Diseases
(Phone 608-267-0249)  (Fax 608-261-4976)

Last Revised: October 30, 2014