SIOUX FALLS, S.D. — South Dakota health officials have detected the first known human case of West Nile virus in the state, in Walworth County, the state Department of Health reported Friday, July 23.

The virus was found in a man in his 60s who is a resident of the county, officials said. The virus was first detected in mosquito pools in Brookings and Codington counties last week, and has since detected in Hughes and Lincoln counties.

Historically, South Dakota has seen a disproportionately high number of West Nile virus cases that involve inflammation of the brain or spinal cord compared to other states in the region, according to the Department of Health. The virus can cause fever, headaches, rash, swollen lymph nodes and muscle and joint aches.

“Protecting yourself from mosquito bites, especially during evening hours, remains vitally important to avoid becoming infected with West Nile Virus,” said Dr. Joshua Clayton, the state epidemiologist, in a news release.

Since its first human West Nile virus case in 2002, the state has reported 2,634 human cases, including 850 hospitalizations and 46 deaths. Every county has reported cases.

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Nationwide, 11 cases have been reported including in North Dakota, Iowa, Arkansas, Texas and Arizona as of July 13, according to the Department of Health. One West Nile fatality, in California, was reported two weeks ago.

Models currently predict South Dakota will have 70-75 cases of West Nile virus cases this year, considered a moderate amount.

Those at high risk for West Nile Virus, including individuals over age 50, pregnant women, organ transplant patients, individuals with cancer, diabetes, high blood pressure or kidney disease and those with a history of alcohol abuse, should be extra vigilant about taking precautions, and anyone with severe or unusual headaches should see a physician, the department said.

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. The species Culex Tarsalis is the primary carrier of West Nile virus 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
  • Support local mosquito control efforts

For more information on West Nile virus and prevention steps, visit the state Department of Health's website, DOH.SD.GOV.