Favorable Conditions for West Nile Virus Mosquito Season

Published on July 02, 2019

Mosquito on leaf

Weld County — The Weld County Health Department continues to take proactive measures in monitoring for West Nile Virus (WNV). A vector index calculation is used to determine human risk for infection. The vector index is currently low and there are no reported human cases of WNV infection. However, the vector index is likely to increase in the ensuing weeks, which means the risk for human infection increases. The number of Culex mosquitoes, which carry WNV, is also increasing.

A Health Department contractor monitors mosquito traps on a weekly basis in three zones of Weld County: the Greeley and Evans area (Zone 1); the Johnstown, Milliken, and Platteville area (Zone 2); and the Firestone, Dacono, and Fort Lupton area (Zone 3). “The increasing hot weather and afternoon thundershowers create favorable conditions for the Culex mosquito that carries WNV,” said Mark E. Wallace, MD, MPH, Executive Director of the Weld County Health Department. “With the holiday weekend and other summer events, it’s extremely important to avoid getting bit by mosquitoes.” Many municipalities have established mosquito control programs, but “the public needs to be vigilant, because WNV has a permanent summer presence in Colorado,” Wallace  said.

West Nile Virus symptoms can appear 3 to 14 days after an infection. 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, he or she should see a health care professional immediately. There are no medications to treat or vaccines to prevent WNV. Less than one percent of infected people develop a serious, sometimes fatal, neuro-invasive illness. Health officials recommend following 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 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 and pants, and a hat, in areas where mosquitoes are active.

For more information about preventing mosquito bites and WNV, click on "Health Hot Topics" at https://www.weldgov.com/departments/health_and_environment.