State and local health officials confirmed the first detections of West Nile Virus in Montana for summer 2025. Virus activity appears to be widespread across the state, and the Department of Public Health and Human Services is urging all Montanans to take increased precautions against mosquito bites.

State and local health officials confirmed four detections of West Nile virus in Montana on Tuesday. There are three pools of mosquitoes in Lewis and Clark County and one pool in Cascade County.

The agency announced this week that four mosquito pools across two counties have tested positive, along with three infected horses.