POLK COUNTY, Wisconsin — The Polk County Health Department was recently notified that a bird in Polk County tested on 7/18/2025 was positive for West Nile virus (WNV) and is reminding people to protect themselves from mosquito bites. The presence of a bird with WNV confirms there are mosquitoes in the area infected with WNV that can spread the virus to people and other animals. Previous WNV infections in people and mosquitoes have already been reported in the state this year.
WNV is spread to humans and other animals through the bite of an infected mosquito. Mosquitoes acquire WNV by feeding on infected birds. The virus is not spread from person to person, animal to animal, or animal to person.
Most people (80%) who are infected with WNV do not get sick. Those who do become ill usually experience mild symptoms such as fever, headache, muscle ache, rash, and fatigue. However, some people (less than 1%) who become infected with the virus get seriously ill with symptoms that include high fever, muscle weakness, stiff neck, disorientation, mental confusion, tremors, confusion, paralysis, and coma. Older adults and those with compromised immune systems are at greater risk of developing severe illness that can be fatal. It is important that people contact a health care provider if they suspect they have WNV illness.
Public Health officials in Wisconsin have monitored the spread of WNV since 2001. An average of 18 human cases of WNV are reported among Wisconsin residents each year. WNV infections in humans have been reported from June through October; however, most people with WNV reported becoming ill in August and September.
The best way to avoid illnesses spread by mosquitoes is to reduce exposure to mosquitoes and eliminate mosquito breeding sites. Mosquitoes will no longer be active once there is a hard frost (temperatures below 28 degrees for at least four consecutive hours), but until then, people are urged to take measures to protect themselves. The Polk County Health Department recommends the following:
Avoid Mosquito Bites
- Apply an insect repellent with DEET, picaridin, oil of lemon eucalyptus, or IR3535 to exposed skin and clothing.
- Prior to heading outdoors, treat clothing with permethrin; do not apply permethrin directly to skin.
- Consider rescheduling outdoor activities that occur during evening or early morning hours, when mosquitoes are most active.
- Wear long-sleeves, long pants, and socks when outdoors to help keep mosquitoes away from your skin.
Mosquito-Proof Your Home
- Prevent mosquitoes from breeding around your home by removing stagnant water from items around your property.
- Empty standing water that has collected in tin cans, plastic containers, flower pots, discarded tires, roof gutters, and downspouts.
- Turn over wheelbarrows, kiddie pools, buckets, and small boats such as canoes and kayaks when not in use.
- Change the water in bird baths and pet dishes at least every three days.
- Clean and chlorinate swimming pools, outdoor saunas, and hot tubs; drain water from pool covers.
- Make sure window and door screens are intact and tightly-fitted to prevent mosquitoes from getting into your home.
- Trim or mow tall grass, weeds, and vines since mosquitoes use these areas to rest during hot daylight hours.
For more information regarding West Nile Virus, please contact the Polk County Public Health Department at 715-485-8400.
Last Update: Aug 15, 2025 2:13 pm CDT
