Overview

• Wisconsin Department of Health Services confirmed the state’s first human West Nile virus case of 2025 in Barron County while mosquitoes in Milwaukee and Lafayette counties also tested positive.
• Hays County Health Department identified its inaugural 2025 human West Nile infection and noted that humans cannot transmit the virus onward.
• Toronto Public Health and the Public Health Agency of Canada verified Canada’s first locally acquired West Nile virus case this year in an adult resident.
• Health experts warn that most infections are silent but about one in 150 can lead to serious neurologic illness, especially in older adults and immunocompromised individuals.
• Public health agencies are intensifying mosquito surveillance, larvicide treatments, and advising EPA-registered repellents, protective clothing and standing water elimination to curb transmission.