The Kansas Department of Health and Environment has issued a high-risk warning for West Nile virus infections for most of the state. 

The KDHE said Wednesday that 22 human cases of have been reported to KDHE in 2023, including 17 neuroinvasive cases and three deaths. The Kansas Department of Agriculture has also reported seven equine cases of WNV this year. Confirmed equine cases have been reported in Barber, Butler, Douglas, Ford and Pratt counties.

West Nile virus is carried and transmitted by mosquitoes and can infect humans, horses, birds and other species. Most infections occur in the late summer and early fall. All but the state's southeast region is at high risk. 

West Nile risk assessment map for Kansas on September 13, 2023. (KDHE)
West Nile risk assessment map for Kansas on September 13, 2023. (KDHE)  

The KDHE said in a release that most people infected with West Nile will not feel sick, but about one in five people who are infected develop a fever and other symptoms. About 1 out of 150 infected people develop neuroinvasive disease, which includes swelling of the brain and/or brain tissue and, in some cases, death.

There are no vaccines or medications to prevent or treat West Nile in humans. Treatment consists of supportive care.

“We’re right in the middle of our peak timeframe for WNV transmission here in Kansas, and with more widespread virus activity this year than in the previous several years, it’s important to take mosquito bite prevention measures to protect yourself, your family, and livestock against all mosquito-borne illnesses,” said Dr. Erin Petro, state public health veterinarian.

KDHE recommends taking the following actions to prevent mosquito bites:

  • When enjoying the outdoors, use insect repellents that contain DEET or other EPA-approved repellents, including picaridin, oil of lemon eucalyptus, or IR3535. When used as directed, EPA-approved insect repellents are proven safe and effective, even for pregnant and breastfeeding women.
  • Individuals should cover their skin with clothing when outdoors, wearing long sleeves and pants when practical.
  • Mosquitoes bite during the day and night, but some species are more active at dusk and dawn. Limit outdoor activities during these peak mosquito activity times.
  • Use screens on windows and doors—repair holes in screens to keep mosquitoes outdoors.
  • Eliminate sources of standing water, which are important breeding sites for mosquitoes—empty standing water from tarps, old tires, buckets and other places where rainwater collects. Refresh water for bird baths, pet bowls, and wading pools at least every three days and consider using larvicide in low-lying areas where water cannot be removed.
  • Talk with a veterinarian about vaccinations to protect horses against WNV.

For more information about West Nile and mosquito bite prevention, visit the KDHE WNV website and check the current regional WNV risk levels, which are updated each Friday from June through October.

For more information about animal diseases, including WNV, visit the KDA Division of Animal Health website.