South Dakota Flu Season Winds Down After 25 Deaths, 16K Cases

PIERRE, S.D. (AP) — The South Dakota Department of Health announced Tuesday that the 2025-2026 influenza season is winding down after peaking in early February, with 16,670 lab-confirmed cases and 905 hospitalizations as of March 25. The season, driven by the aggressive Influenza A (H3N2) strain—particularly the K subclade variant—proved more severe than the eight-year average of 12,504 cases and 690 hospitalizations. State epidemiologist Dr. Ryan Clayton noted an average of 40 annual flu deaths, but this year recorded 25, including the first two in Minnehaha County on Dec. 31, both residents over 64.

Nationally, the CDC classified the season as 'moderately severe,' with South Dakota aligning closely: peak combined respiratory hospitalizations for flu, COVID-19 and RSV hit during the week ending Jan. 3, 2026, at levels within 20% of the prior year. Vaccine effectiveness dipped due to antigenic drift in the H3N2 variant that emerged post-vaccine formulation, yet officials stress it still cuts severe outcomes. By late March, acute respiratory illness visits statewide fell to low levels, per CDC surveillance.

Rural Northeast South Dakota clinics bore heavy strain, mirroring statewide trends of elevated activity above norms. The DOH dashboard shows influenza declining sharply from the February peak week. 'Don't let your guard down,' urged Clayton, recommending handwashing, avoiding sick contacts and staying home if ill—especially as spring weather mixes with residual virus circulation in communities from Sioux Falls to Watertown.

As of May 4, 2026, health leaders continue pushing vaccinations for at-risk groups, noting H3N2's toll on the elderly and young children. This season's data underscores South Dakota's vulnerability in high-risk years, with officials preparing for next fall via updated surveillance.