Grant County, WA – Grant County Mosquito Control District No. 1 (GCMCD1) has detected West Nile virus (WNV) in mosquitoes collected near Crab Creek north of Moses Lake. The mosquitoes were collected during routine testing on August 24, 2025, and the positive result was confirmed at Oregon Veterinary Diagnostic Laboratory on September 3, 2025. It is possible there could be mosquitoes carrying the virus in other areas.
“Although most people will not get seriously ill from West Nile virus, we do not want anyone to get sick because of a mosquito bite,” said Amber McCoy, GCHD Investigation & Response Manager. “If you’re enjoying activities outside, be sure to take the necessary steps to fight the bite.”
Current Situation
Grant County is the third county in Washington to report detections of WNV this year. Benton and Yakima counties have previously reported positive mosquito samples.
So far in 2025, there have been no reports of people or animals infected with WNV in Washington. Most states in the US, including neighboring states Idaho and Montana, have reported at least one human case this year. In August, the Idaho Department of Health and Welfare confirmed a WNV-related death in an Idaho resident. The last reported human case in Grant County was in 2015.
About West Nile Virus
WNV is the leading cause of mosquito-borne disease in the United States. WNV is spread to people through the bite of an infected mosquito. It mostly occurs during mosquito season, which is summer to fall.
West Nile Virus Symptoms
Most people infected with WNV will not get sick, but in some cases it can be serious. About 1 in 150 people who are infected develop a severe illness affecting the central nervous system that results in encephalitis or meningitis. There is no specific medication for WNV disease, but hospital care may be necessary for severe cases.
You should contact your doctor if you have any of the following symptoms and recently had mosquito bites:
1 in 5 people experience mild symptoms:
Fever and
- Body aches
- Joint pains
- Rash
- Vomiting
- Diarrhea
- Headache
1 in 150 people experience severe symptoms:
- High fever
- Neck stiffness
- Disorientation
- Tremors
- Muscle weakness
- Paralysis
- Coma
- Convulsions
High Risk Groups
You are at higher risk of serious illness from WNV if you are 60 or older, or have certain medical conditions, such as:
- Cancer
- Diabetes
- Hypertension
- Kidney Disease
Prevent West Nile Virus
Take steps to prevent mosquito bites:
- If possible, stay indoors at dawn and dusk. This is when mosquitoes are most active.
- Wear a long-sleeved shirt, long pants, and a hat when going into areas with mosquitoes.
- Use an EPA-registered mosquito repellent when spending time in areas with mosquitoes.
- Apply children’s repellent for them.
- Mosquito repellents that contain the active ingredients DEET, Picaridin, IR3535, or oil of lemon eucalyptus work best.
- Treat clothing and gear with permethrin to kill or repel mosquitoes.
- Make sure windows and doors are “bug tight” and repair or replace screens as needed.
- Eliminate mosquito-breeding areas around your home. Empty anything that holds standing water—bottles, cans, old tires, buckets, trash containers, plastic covers, planters, and toys.
- Change water in birdbaths, fountains, kiddie pools, and animal troughs at least twice each week.
- Make sure roof gutters drain properly. Clean clogged gutters in spring and fall.
- Fix leaky outdoor faucets and sprinklers.
At-Risk Animals
Birds and equine animals (e.g., horses, donkeys, mules) can get WNV. Infected animals can get very sick, which commonly results in death. Equine owners should ask their veterinarian about the WNV vaccine.
GCMCD1 Control Efforts
GCMCD1 began their annual mosquito control efforts in March 2025 and will continue through October 2025. So far this season, GCMCD1 has set 1,494 adult mosquito traps and tested over 869 mosquito samples.
Grant County has three mosquito control districts. Grant County Mosquito Control District No. 1 serves the greater Moses Lake area (see map to the left), while the other two districts cover the Coulee City and Electric City/Grand Coulee areas. Each district conducts mosquito control efforts within its set boundaries. Some parts of the county are not within the boundaries of a mosquito control district.
“We will continue to target both larval and adult mosquitoes in an effort to reduce the spread of the virus to other areas of the district” added Ann Belchik-Moser, District Manager of GCMCD1.
For more information about mosquito control efforts in Grant County, visit https://www.gcmcd1.org/.
For more information about WNV, visit https://granthealth.org/207/West-Nile-Virus.
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