South Dakota Reports First West Nile Virus Death of 2026 as Cases and Mosquito Activity Rise

Northeast Radio SD News – South Dakota  - The South Dakota Department of Health is reporting two human cases of West Nile virus so far this season, according to its latest surveillance update released July 17. The cases were identified in Jerauld County and Pennington County, with one classified as non‑neuroinvasive and the other as neuroinvasive, the more severe form of the disease. The neuroinvasive case resulted in one death, according to the report.

State health officials also noted no viremic blood donor detections to date. They confirmed two counties — Brown and Hughes — have reported positive mosquito pools, indicating active virus circulation in mosquito populations.

Case Outlook for 2026

The Department of Health’s predictive model currently estimates 58 human cases for the 2026 season. Historical comparison charts included in the update place 2026 in a moderate‑risk range similar to years such as 2017, 2022, and 2014.

National West Nile Activity

Across the United States, 81 human cases have been reported so far this year, 57 of which are neuroinvasive, according to data compiled from the Centers for Disease Control and Prevention.

Mosquito Surveillance in South Dakota

Mosquito surveillance continues statewide, with 46 collection sites operating this season. As of July 16, the state has tested 261 mosquito pools, identifying a 3.83% positivity rate among 12,416 Culex species collected — the primary mosquito species responsible for transmitting West Nile virus.

Weekly surveillance charts show fluctuating mosquito pool testing numbers and rising Culex counts as the season progresses, with notable increases beginning around MMWR Week 23.

Health Officials Urge Precautions

With mid‑summer conditions favoring mosquito activity, health officials encourage residents to reduce exposure by using insect repellent, wearing protective clothing, and eliminating standing water around homes.

More information is available through the South Dakota Department of Health’s West Nile virus resources.

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