Northern Colorado health officials confirm first West Nile Virus case in Weld County

On Monday, health officials in Northern Colorado confirmed the first case of West Nile Virus found in Weld County this year.

The Weld County Department of Public Health and Environment says the first case of 2026 comes one month later than it did in 2025. Health officials said they investigated 35 cases of West Nile in Weld County last year.

Fortunately, the number of trapped Culex mosquitoes responsible for transmitting the virus is at a five year low. However, approximately 80% of the ones captured have been in three zones which cover areas including:

• The Greeley, Evans, Kersey, LaSalle area
• The Johnstown, Milliken and Platteville area
• The Firestone, Dacono and Fort Lupton area

Residents are encouraged to drain standing water around their homes every week and avoid outdoor activities during dusk and dawn, when the mosquitoes are more active. They encourage the public to use insect repellents containing DEET, picaridin, IR3535, lemon eucalyptus oil or para-menthane-diol. Residents should also wear long sleeves, pants and hats when outside.

West Nile symptoms typically appear between three and 14 days after infection. Although many people do not show symptoms, those infected might experience fever, headache, nausea and vomiting, muscle aches, weakness and/or a rash. The WCDPHE said anyone who develops symptoms is encouraged to see a medical professional immediately.