HELENA — State and county health officials have confirmed the first detections of West Nile virus in Montana for 2025.
Four mosquito pools have tested positive for West Nile, including three in Lewis and Clark County and one in Cascade County. Additionally, Sheridan, Custer, and Daniels Counties have each reported one confirmed case of the virus in horses, totaling three positive horses in Montana so far this season.
According to the Department of Public Health and Human Services, virus activity appears to be widespread across the state. DPHHS is urging all Montanans to take increased precautions against mosquito bites.
“Illness caused by WNV can vary significantly in severity,” said DPHHS Vectorborne Disease Epidemiologist Devon Cozart. “Although some people may not experience any symptoms at all, many people experience the onset of flu-like symptoms such as body aches and fatigue that may persist for weeks to months. Severe, neurological cases of WNV also occur every year in Montana, which may lead to death or permanent disability like blindness or paralysis. Don’t take a chance; prioritize avoiding mosquito bites whenever possible.”
Currently, there is no vaccine or targeted medication for West Nile virus in humans, aside from supportive care. Most people who become infected with the virus will be asymptomatic, but 1 in 5 experience mild symptoms, including headache, rash, body aches, joint pains, fatigue, vomiting, and diarrhea. Fatigue and body aches may persist for weeks following infection.
About 1 in 150 human infections result in severe disease, which can cause neurological symptoms, including disorientation, stupor, coma, paralysis, vision loss, and convulsions. The virus can be fatal or lead to long-term neurological complications.
