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As of September 30, 2025, there have been a total of 1,324 human cases of West Nile virus reported in 42 states this year, according to the Centers for Disease Control and Prevention (CDC). This compares with 1,791 cases for all of 2024, but it’s far below the 9,862 cases reported in 2003—the highest incidence across the past 25 years. Colorado has been particularly hard hit with 235 cases and 12 deaths this year, according to state health department data.Â
Almost out of the woods: The typical West Nile virus season runs May through October. Clinical management is supportive, although no medicines are available to treat or prevent the disease. Instead, CDC recommends community-level mosquito control programs and offers information on clinical signs and symptoms to watch for on its website.