West Nile Virus in Montana
West Nile Virus is showing early 2026 season activity across multiple states before the typical transmission season begins. Positive mosquito pools have been confirmed in Texas (San Antonio, Frisco), Louisiana (New Orleans), and six California counties. Human cases have already been confirmed in Colorado. Peak transmission season runs July through September — and an above-average season is projected for 2026. Most infections are mild or asymptomatic, but about 1 in 150 infected people develop severe, potentially fatal brain inflammation.
No active West Nile Virus reports in Montana right now.
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What is West Nile Virus?
West Nile Virus arrived in the U.S. in 1999 and has since become the leading mosquito-borne disease in the country. It's transmitted by Culex mosquitoes that bite infected birds. While 80% of infected people have no symptoms, severe cases can cause encephalitis or meningitis with long-term neurological effects. Age over 60 significantly increases risk of severe disease.
Symptoms
- Mild (West Nile fever): Fever, headache, body aches, joint pain, vomiting, diarrhea, rash
- Severe: High fever, severe headache, stiff neck, disorientation, tremors, seizures
- Neurological: Muscle weakness, vision loss, paralysis, coma
- Long-term effects: Fatigue, memory problems, muscle weakness (can persist months/years)
Transmission
Transmitted through bites of infected Culex mosquitoes. Rarely through blood transfusion, organ transplant, mother to fetus, or breastfeeding. NOT spread person-to-person through casual contact.
Contagious Period: Not contagious person-to-person; can be in blood of infected person during illness
Prevention
- Use EPA-registered insect repellents (DEET, picaridin, IR3535, oil of lemon eucalyptus)
- Wear long sleeves and pants at dawn/dusk when mosquitoes most active
- Install/repair window and door screens
- Use air conditioning when possible
- Eliminate standing water (buckets, flower pots, bird baths, gutters)
- Change water in pet bowls, birdbaths weekly
- Treat or drain swimming pools, fountains
- Community mosquito control programs (spraying, larvicides)
- Avoid outdoor activities at dawn/dusk during peak season
Montana Health Resources
Local health department information and state-specific prevention guidance
We're Monitoring Montana
Our AI-powered surveillance continuously monitors West Nile Virus activity across Montana. We track data from state health departments, local hospitals, CDC reports, and 50+ global health sources to provide early warning of emerging threats.
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Montana Health Department
For official state health alerts, vaccination locations, and public health guidance specific to Montana, visit your state health department's website.
Understanding West Nile Virus: Key Questions
Whether you live in Montana or are traveling there, knowing the symptoms, timeline, and when to seek care helps you act quickly if exposure occurs.
When to Seek Care
Seek care if you experience severe dehydration, bloody stools, high fever, or symptoms lasting more than 3 days. Children under 5, adults over 65, and immunocompromised individuals should seek care earlier.
Emergency symptoms: Severe dehydration, inability to keep fluids down for 12 or more hours, or neurological symptoms require emergency care.
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Expert Resources & References
Trusted information from leading health organizations
CDC
Official guidance from the U.S. Centers for Disease Control and Prevention
View CDC Resources →WHO
Global disease surveillance and guidelines from the World Health Organization
View WHO Resources →Medically Reviewed Content
Disease information on Virus Watcher is reviewed by our Chief Epidemiologist, a former CDC lead analyst for FluSight forecasting. Outbreak data is aggregated from verified sources including BEACON, ProMED, WHO, CDC, and 50+ national health agencies. This information is for educational purposes and should not replace professional medical advice.
Last reviewed: 2026-07-18
Recent West Nile Virus Reports
No confirmed cases reported in Montana yet. Here are the latest West Nile Virus reports from our global surveillance network.
Virus Watcher monitors Google search trends as an early warning signal. Research shows disease-related searches typically spike 2 to 6 weeks before clinical cases peak, giving communities early notice before hospital data catches up. **West Nile Virus**: Search interest is 2.47x…
It's been quite the start to the summer season -- weeks of dangerous heat, hazardous air quality due to Canadian forest fires, a parasite causing "explosive diarrhea" sweeping Illinois and, in Lake County, the first detection of the West Nile virus. But while the mosquito-borne …
Los Angeles County public health officials announced Monday the first confirmed human case of West Nile virus in the county this year, involving an Antelope Valley resident who was hospitalized after developing a severe neurological illness. The patient began experiencing sympto…
Dean Fioresi is a web producer for CBS Los Angeles. He covers breaking news throughout Southern California. When he's not writing about local events, he enjoys focusing on sports and entertainment. Long Beach city officials have confirmed California's first human case of West Ni…
Officials are increasing mosquito trapping and urging residents to avoid standing water NEWYou can now listen to Fox News articles! are urging residents to protect themselves from mosquito bites after was detected in mosquitoes for the first time this year. The Metro Public He…
Dan Raby, the senior digital producer for CBS News Atlanta, has been covering everything happening around Georgia for more than a decade. A group of mosquitos caught in an area of Atlanta have tested positive for West Nile virus, the Fulton County Board of Health reports. Autho…
Add Yahoo as a preferred source to see more of our stories on Google. Much of the country is sizzling under record heat, but Dr. Peter Hotez, an infectious disease specialist in Houston, is heading out for his early morning walks as covered up as possible in a t-shirt, a hooded …
Adam Harrington is a digital producer at CBS Chicago, where he first arrived in January 2006. The North Shore suburb of Wilmette this week became the latest Chicago-area municipality to discover mosquitoes carrying the West Nile virus this year. The North Shore Mosquito Abateme…
Frequently Asked Questions
Common questions about West Nile Virus answered by our epidemiology team
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