https://dphhs.mt.gov/News/2025/July/WestNileVirusActivity West Nile Virus Activity Confirmed in Montana

DPHHS urges Montanans to take increased caution against mosquito bites this summer

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

Four mosquito pools have tested positive for WNV, including three in Lewis and Clark County and one in Cascade County. Detection of WNV in mosquitoes is an early indicator that activity is increasing within the state, elevating the risk of human illness.  Additionally, Sheridan, Custer, and Daniels Counties have each reported one confirmed case of WNV in horses, totaling three positive horses in Montana so far this season.

WNV can cause illness in humans after a bite from an infected Culex mosquito. The increased risk of transmission to humans is expected to continue through October, or as long as mosquitoes remain active in the state.

“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 WNV in humans, aside from supportive care. Most people who become infected with WNV 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, referred to as neuroinvasive West Nile. Neuroinvasive West Nile can cause neurological symptoms, including disorientation, stupor, coma, paralysis, vision loss, and convulsions. WNV can be fatal or lead to long-term neurological complications.

Horses can also be infected with WNV. Horse owners may contact their veterinarian to obtain an annual vaccine to protect against WNV.

Preventing mosquito bites is important while spending time outdoors in the summer, especially during dusk and dawn, which are peak feeding activity times for female Culex mosquitoes. Permethrin is an insect repellent that can be utilized to treat clothing and gear, including tents. The Environmental Protection Agency also maintains lists of approved insect repellents that can be applied directly to the skin.

Emptying standing water at least once per week is important to keep mosquitoes away from homes. For items such as rain barrels, apply a screen to the opening to restrict mosquito access.

For other mosquito bite prevention tips, check out the 4 Ds of mosquito bite prevention below.

The 4 Ds of Mosquito Bite Prevention include:

• DEET: Use insect repellent containing effective ingredients such as DEET or picaridin. To verify the effectiveness of insect repellent, go to the EPA’s website: epa.gov/insect-repellents.

• Drain: Drain standing water around the house to prevent mosquito breeding.

• Dawn/Dusk: Mosquitoes are most active during dawn and dusk. Stay inside or take extra precautions to prevent mosquito bites during these times. If doors or windows are left open in the summer, make sure they’re fitted with screens to keep mosquitoes out of the house.

• Dress: When possible, wear long-sleeved shirts and pants to protect against bites.

Contact your local health department or visit https://dphhs.mt.gov/publichealth/cdepi/diseases/WestNileVirus for more information about WNV protection and surveillance activities.

Current Measles Information

 KPAX News Release at this Youtube link.

https://www.youtube.com/watch?v=P8XhRDvLSYA

UPDATE July 24, 2025 A case of measles in a child in Yellowstone County was reported. The child was unvaccinated and attended Vacation Bible School during the infectious period, exposing approximately 80 people. A second case related to the first one was reported.

UPDATE July 17, 2025 A case of measles in Cascade County was reported in an adult.

UPDATE July 10, 2025 NO further measles cases have been reported since late June.

UPDATE JUNE 18, 2025 More cases reported in MT. Yellowstone, Gallatin, Hill and Flathead Counties bringing the total to 20 cases.

UPDATE MAY 28, 2025 A case of measles has been reported out of Hill County, MT. Another case also in Gallatin County has been reported.

UPDATE MAY 21. 2025. A case of measles in an adult in Flathead County has been reported. The patient had a travel history but more information is being gathered on that travel and vaccination status.

On April 17, 2025, 5 confirmed measles cases were reported in Montana. On April 29, 2025, 2 more confirmed measles cases were reported, who were household contacts of the original cases. On May 5, 2025, 1 more confirmed measles case was reported, also a household contact to the original cases. This brings the total to 8 cases of measles; all are residents of Gallatin County. The three secondary cases were not immunized against measles, and were isolating at home when they became ill. There have been no additional public exposure locations identified and there is no evidence of community transmission. Prior to this, no cases of measles were reported in Montana since 1990.

WHAT IS MEASLES?

Measles is a serious respiratory disease caused by a virus. Measles starts with a fever. Soon after, it causes a cough, runny nose, and red eyes. Then a rash of tiny, red spots breaks out. It starts at the head and spreads to the rest of the body. The rash can last for a week, and coughing can last for 10 days. CDC: Measles cases and outbreaks 

HOW IS MEASLES SPREAD?

Measles is highly contagious and spreads through the air when an infected person coughs or sneezes. It is so contagious that if one person has it, 9 out of 10 people around him or her will also become infected if they are not protected.

• You can get measles just by being in a room where a person with measles has been, even up to two hours after that person has left.

• An infected person can spread measles to others even before he or she develops symptoms—from four days before they develop the measles rash through four days afterward.

• For more information on transmission, see: CDC: Measles transmission

POSSIBLE EXPOSURE TO MEASLES?

If you’re not protected against measles and think you might have been exposed to someone with measles:

• Stay home. Do not go straight to the doctor. Instead, call ahead to inform a healthcare professional of your possible exposure so you can get instructions about how to avoid exposing others.

• If you’re not already protected, get a measles vaccine.

  • If given within 72 hours of initial exposure, MMR vaccine may provide some protection or lessen the severity of disease.

  • Except in healthcare settings, unvaccinated people who receive their first dose of MMR vaccine within 72 hours after exposure may return immediately to childcare, school, or work.

COMPLICATIONS OF MEASLES

Measles can cause serious health complications, such as pneumonia or encephalitis, and even death.

• Children younger than 5 years of age and adults older than 20 years of age are at high risk of getting a serious case of measles.  When you get vaccinated, you also protect others around you who are at high risk for complications but can’t get vaccinated because they are too young or have a health condition.

• About 1 in 4 unvaccinated people in the U.S. who get measles will be hospitalized; 1 out of every 1,000 people with measles will develop brain swelling (encephalitis); 1 or 2 out of 1,000 people with measles will die, even with the best care.

• For more information on complications, see: CDC: Measles complications

VACCINATION RECOMMENDATIONS

The best protection against measles is MMR vaccine. MMR vaccine provides long-lasting protection against all strains of measles. Make sure you’re up to date on MMR and other vaccinations.

• Parents should make sure their children are protected against measles with two doses of MMR vaccine–the first dose at 12 through 15 months of age and the second dose 4 through 6 years of age.

• For more information on vaccination, see: Montana Immunization Program and CDC: Measles vaccination

PLAN FOR TRAVEL

https://dphhs.mt.gov/publichealth/cdepi/diseases/Measles

• Travel Health (mt.gov)

• Travel Vaccines (mt.gov)

• Plan for Travel - Measles | CDC

• Travel: Check If You’re Protected Against Measles | CDC