First 2021 West Nile cases confirmed in Larimer, Delta Counties

Local News

LARIMER COUNTY, Colo. (KDVR) – Health officials have confirmed two human West Nile cases in Larimer and Delta Counties.

A Berthoud resident is the Larimer County case. Officials have not said in which town the Delta County case was confirmed.

The Larimer County Department of Health and Environment (LCDHE) and the Colorado Department of Public Health and Environment (CDPHE) verified the cases.

CDPHE said both cases have survived and are recovering from their illnesses at the time of the investigation.

LCDHE said mosquito numbers are abundant in many areas of the county, and that human case reports usually peak in August and September.

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% of people who are infected don’t have any symptoms; about 25% will develop West Nile fever, which may progress to severe neuroinvasive infection. This may lead to hospitalization, critical illness, chronic disability or even death.

Colorado has had cases of West Nile virus every year since 2002.

Trapping mosquitoes to monitor for West Nile virus risk began in June in Larimer County. Larimer County Department of Health and Environment works with local cities and towns, a mosquito abatement company (Vector Disease Control International), and Colorado State University to monitor and assess the risk to Larimer County residents.

Experts say West Nile virus can be prevented. That can easily be done by using an effective repellent or staying indoors when mosquitoes are most active, between dusk and dawn. 

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 D’s to help prevent West Nile virus disease:

  • Defend – 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 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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