Weld County Identifies First Two Human Cases of West Nile Virus

Published on September 02, 2019

Mosquitoes in petri dish

Weld County — Two adults have been identified as the first human cases of West Nile Virus (WNV) for the 2019 mosquito season in Weld County. Both adults are recovering at home and neither was hospitalized. Mosquito traps in Weld County found the vector index — a calculation to determine human risk for WNV infection — has increased. A vector index that exceeds 0.75 indicates an increased risk for human infection. The vector index for Aug. 18-24 was 0 for Zone 1 and 2 and 0.20 for Zone 3. The vector index for Aug. 25-31 was 0.64 for Zone 1, 0.94 for Zone 2, and 0.46 for Zone 3.

“Even though summer is ending soon, the public still needs to prevent mosquito bites,” said Mark E. Wallace, MD, MPH, Executive Director of the Weld County Health Department. “Keep following the '4 Ds' for prevention to avoid getting bit by mosquitoes.” Many municipalities have established mosquito control programs, but “the public needs to remain vigilant until the first hard frost in late September or early October which knocks the mosquito population way down,” Wallace said.

West Nile Virus symptoms can appear 2-14 days after a bite from an infected mosquito. Initial symptoms can include fever, headache, nausea and vomiting, muscle aches and weakness, and rash, but most infected people don’t exhibit any symptoms. If a person develops symptoms, they should see a health care professional immediately. There are no medications to treat or vaccines to prevent WNV infection. Less than one percent of infected people develop a serious, sometimes fatal, neuroinvasive illness. Health officials recommend following the "4 Ds” 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 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  also are effective against mosquitoes. Always follow label instructions carefully.
  • DRESS in long sleeves and pants in areas where mosquitoes are active.

All vector index results are updated weekly by Weld County health officials.