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West Nile Virus Update: Sept. 17, 2021

A gauge showing the West Nile virus prediction model for the total number of cases predicted for the 2021 season in South Dakota; 117 cases predicted for the 2021 season in South Dakota.
Figure 1. West Nile virus prediction model for the total number of cases predicted for the remainder of the 2021 season in South Dakota. Updated Sept. 13, 2021. Courtesy: South Dakota Department of Health.

Originally Submitted: Sept. 17, 2021

As of Sept. 15th, the South Dakota Department of Health indicated that West-Nile-virus-positive mosquitoes were detected in Beadle, Brookings, Brown, Codington, Hand, Hughes, Lincoln and Minnehaha counties in South Dakota. So far, there have been 36 reported human cases of West Nile virus from Beadle, Bon Homme, Brown, Clark, Davison, Day, Dewey, Douglas, Hamlin, Hand, Hughes, Hutchinson, Kingsbury, Lake, Lawrence, Minnehaha, Moody, Oglala Lakota, Potter, Roberts, Sanborn, Spink, Stanley, Tripp, Union, Walworth and Yankton counties. Although human cases are still low, the SD DOH is now predicting an outbreak of West Nile virus cases (117 cases predicted) (Figure 1).

Even though case numbers are currently low, it’s important to remember that evening activities should be monitored, and an attempt to avoid mosquito bites should be made. As mentioned in our previous article, Will Mosquitos Be an Issue During This Summer?,there are two mosquitos that account for most of the human bites and the risk associated with contracting the West Nile virus. Another of our previous articles, Enjoying the Outdoors Without Tick and Mosquito Bites, discusses practices that can reduce mosquito bites.

There has been a noticeable increase in mosquito activity in many areas of South Dakota. This is likely due to precipitation that was received in these areas a week to 10 days ago. One step in reducing mosquito populations is to ensure that there is no standing water in old tires, buckets, gutters or anything that can serve as a container. Mosquitos utilize these habitats and removal can help reduce mosquitos.

If you are outside at dusk or after dark, make sure to cover as much of your skin as possible by wearing long sleeves and pants. We also recommend using insect repellants that contain DEET or similar active ingredients to provide further protection. The U.S. Environmental Protection Agency provides a helpful tool for choosing a repellant that will provide the best protection based on the desired activities.

Mosquitos will continue to be a threat until after one or two hard frosts. Precautions and actions to avoid bites should be continued until that time.

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