First Human Case of West Nile Virus in Wisconsin

Continue to prevent mosquito bites until the first hard frost

The Wisconsin Department of Health services (DHS) is reminding people to protect themselves from mosquito bites following the first confirmed human case this year of West Nile virus (WNV) in a Sheboygan County resident. Despite cooler temperatures, mosquito activity and the risk of WNV will continue until the first hard frost (temperatures below 28 degrees for at least four consecutive hours). Cases of WNV have also been reported in three animals in Wisconsin, two horses and a bird. These animal cases were located in Trempealeau, Monroe, and Milwaukee counties.

“This report of the first case of West Nile Virus in a person is a reminder of the continued importance of taking precautions to prevent mosquito bites and the viruses they carry as we move into the fall,” said State Health Officer Paula Tran. “While West Nile virus and other viruses spread by mosquitoes pose a risk to all Wisconsinites, people who have weakened immune systems are at the greatest risk for serious illness.”

WNV is spread to humans, horses, birds, and other animals through the bite of an infected mosquito. Mosquitoes acquire WNV by feeding on infected birds. The virus is not spread directly from person to person, animal to animal, or animal to person.

The best way to avoid illnesses spread by mosquitoes is to reduce exposure to mosquitoes and eliminate mosquito breeding sites. DHS and Sheboygan County Health and Human Services offer these tips to protect yourself and your family against mosquito bites.

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 that spread WNV are most active.
  • Wear long sleeves, long pants, and socks when outdoors to help keep mosquitoes away from your skin.

Mosquito-Proof Your Home

  • Make sure window and door screens are intact and tightly-fitted to prevent mosquitoes from getting into your home.
  • Prevent mosquitoes from breeding around your home by removing stagnant water from items around your property, such as 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.
  • Trim or mow tall grass, weeds, and vines since mosquitoes use these areas to rest during hot daylight hours.

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. For those without a provider, help is available by dialing 211 or 877-947-2211, or texting your ZIP code to 898-211 for free, confidential support.

Since WNV was first detected in Wisconsin in 2002, infections in humans have been reported from June through October; however, most people with WNV report becoming ill in August and September.

To learn more about WNV and other diseases that can be spread by mosquitoes and how to protect yourself, visit the DHS website.