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First Human West Nile Virus Detection of 2021 Reported in Walworth County

For Immediate Release: July 23, 2021

Contact: Daniel.Bucheli@state.sd.us



First Human West Nile Virus Detection of 2021
Reported in Walworth County


PIERRE, S.D. – Today, the South Dakota Department of Health confirmed that a Walworth County resident, a male in his 60’s, is South Dakota’s first human West Nile virus (WNV) case of the 2021 season.


“Protecting yourself from mosquito bites, especially during evening hours, remains vitally important to avoid becoming infected with West Nile Virus,” said Dr. Joshua Clayton, State Epidemiologist.


Historically, South Dakota has seen a disproportionately high number of WNV cases that involve inflammation of the brain or spinal cord compared to other regional states. Residents can reduce their risk by taking the following actions:


  • Apply mosquito repellents (DEET, picaridin, oil of lemon eucalyptus, 2-undecanone, param-menthane-diol, or IR3535) to clothes and exposed skin. Limit exposure by wearing pants and long sleeves in the evening;
  • Limit time outdoors from dusk to midnight when mosquitoes are most active. Culex tarsalis are the primary carrier of WNV in South Dakota;
  • Remove standing water that gives mosquitoes a place to breed. Regularly change the water in birdbaths, outside pet dishes, and drain water from other flowerpots and garden containers and stay away from areas near standing water; and
  • Support local mosquito control efforts.


These precautions are especially important for people at high risk for WNV, including individuals over 50, pregnant women, organ transplant patients, individuals with cancer, diabetes, high blood pressure or kidney disease, and those with a history of alcohol abuse. People with severe or unusual headaches should see their physicians.


Since the first human WNV case was reported in 2002, the state has reported 2,634 human cases, including 850 hospitalizations and 46 deaths. Every county has previously reported cases.

For more information on WNV and other health-related items, visit DOH.SD.GOV.