Harmful Algal Bloom Statistics

Human Cases

From 2016 to 2025, MDH received reports of 13 Harmful Algal Bloom (HAB)-associated illnesses: 3 suspect cases and 10 probable cases. Case statuses are determined based on the CDC: OHHABS Case Definitions (PDF). The median number of cases annually was 1 (range, 0 to 3). The median age of cases was 15 years (range, 2 to 70 years). All cases were exposed to HABs during May through September, with 37% of cases exposed in July. Two cases were exposed outside of Minnesota.

Animal Cases

From 2016 to 2025, MDH received reports of 12 animal HAB-associated illnesses: 4 suspect cases, 8 probable cases. Case statuses are determined based on the CDC: OHHABS Case Definitions (PDF). The median number of animal cases annually was 1 (range, 0 to 3). All animal HAB-associated illness cases were dogs. All animal cases were exposed to HABs during March through September. Ten (67%) cases died as a result of their illness.

Charts, Graphs, and Maps

	Human HAB-Associated Illness Cases in Minnesota by County of Exposure, 2016-2025 (PDF) Map of the total number of human HAB-associated illness cases in Minnesota from 2016 to 2025 by county of exposure.
	Animal HAB-Associated Illness Cases in Minnesota by County of Exposure, 2016-2025 (PDF) Map of the total number of animal HAB-associated illness cases in Minnesota from 2016 to 2025 by county of exposure.
	Animal and Human HAB-Associated Illness Cases in Minnesota by County of Exposure, 2016-2025 (PDF) Map of the total number of animal and human HAB-associated illness cases in Minnesota from 2016 to 2025 by county of exposure.