Weld County reports first human case of West Nile Virus in 2024

Published on July 18, 2024

Mosquitoes in a petri dish

The Weld County Department of Public Health and Environment (WCDPHE) is investigating a potential case of West Nile Virus (WNV) in a Weld County resident. While this is the first case of the 2024 mosquito season, last year there were 52 cases of WNV investigated in Weld County.

This year, culex mosquito numbers are lower than our 5-year average; however, currently culex mosquitoes are making up about 50% of mosquitoes that are trapped in the three sentinel zones in Weld County, which include the Greeley, Evans, Kersey, LaSalle area, the Johnstown, Milliken, and Platteville area, and the Firestone, Dacono, and Fort Lupton area. These mosquito traps are monitored on a weekly basis and mosquitoes in all three zones have tested positive for WNV. 

Symptoms of WNV can appear three to 14 days after infection. While most infected people do not show any symptoms, initial symptoms can include fever, headache, nausea and vomiting, muscle aches and weakness, and rash. If a person develops symptoms, they should see a health care professional immediately. There are no medications to treat or vaccines to prevent West Nile virus infection. Less than 1% of infected people develop a serious, sometimes fatal, neuroinvasive illness. Health officials recommend the public stay vigilant as WNV has a permanent summer presence in Colorado and follow the four “D’s” to prevent mosquito bites:

  • DRAIN standing water around your house weekly. Remember to drain water from tires, cans, flowerpots, clogged rain gutters, rain barrels, toys, and puddles.
  • DUSK and DAWN are when Culex mosquitoes are most active. Limit outdoor activities and take precautions to prevent mosquito bites during these times.
  • DEET is an effective ingredient to look for in insect repellents. Other repellents containing picaridin, IR3535, oil of lemon eucalyptus, or para-menthane-diol are also effective against mosquitoes. Always follow the product label instructions carefully.
  • DRESS in long sleeves, pants, and a hat in areas where mosquitoes are active.

For more information about preventing mosquito bites and WNV, go to weld.gov/go/zoonosis.

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