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Human West Nile infection in Larimer County

June 22, 2016 | Local News

This week the Larimer County Department of Health and Environment received the first report of a case of West Nile virus (WNV) in Larimer County this year.

A Loveland resident showed symptoms consistent with West Nile virus, and blood tests revealed West Nile virus infection. The resident was not hospitalized. Infection likely occurred the last full week of May.

Trapping of mosquitoes has already begun in some areas of Larimer County. Testing of trapped mosquitoes for West Nile virus will begin next week. Residents will be able to check online ( to see weekly maps showing the number of Culex mosquitoes that were trapped in and around their neighborhoods in several urban areas of the county. If the trapped mosquitoes were tested for West Nile infection, weekly results can be found on a second map. Not all communities test the trapped mosquitoes due to the cost.

West Nile disease is a viral infection which is spread to people by bites from infected Culex mosquitoes. Symptoms can range from none at all to severe illness. About 75 percent of people who are infected are asymptomatic; about 25 percent will develop West Nile fever. Less than one percent develop the more severe neuroinvasive form, which can lead to hospitalization, critical illness, chronic disability, or even death.

Larimer County Department of Health and Environment works with cities, Colorado Mosquito Control, Inc., and Colorado State University to monitor and assess the risk to Larimer County residents. The Health Department also works with homeowner’s associations to provide advice on eliminating sources of mosquito breeding and other methods of mosquito control.

West Nile virus can be prevented. In addition to community efforts, such as larviciding, reducing water where mosquitoes can breed, and spraying for adult mosquitoes, individuals can remember to use the 4 Ds to help prevent West Nile virus disease:

  • DEET or other effective mosquito repellent – Use an EPA-registered mosquito repellent that has been proven to be effective against West Nile virus-carrying mosquitoes. DEET, Picaridin, Oil of Lemon Eucalyptus (also called p-menthane-3,8-diol or PMD) and IR3535 are good choices.
  • Dusk to dawn – Avoid exposure during peak Culex mosquito feeding times, from dusk through dawn.
  • Dress – Wear long sleeves and pants to keep mosquitoes from biting.
  • Drain – Remove standing water in your yard or garden to minimize mosquito breeding areas.

For more tips on what you can do to prevent West Nile virus, visit

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