First Human West Nile Virus Case in Larimer County

The Larimer County Department of Health and Environment (LCDHE) has confirmed the first case of West Nile virus in a Larimer County resident in 2021. The case is a Berthoud resident. Human case reports usually peak in August and September.

Mosquito numbers are abundant in many areas of the county. It is a good time to remind people to protect themselves from the West Nile virus by taking steps to avoid being bitten. That can easily be done by using an effective repellent or staying indoors when mosquitoes are most active, between dusk and dawn.

Trapping mosquitoes to monitor for West Nile virus risk began in June in Larimer County. West Nile disease is a viral infection that 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 a severe neuroinvasive infection. This may lead to hospitalization, critical illness, chronic disability, or even death.

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.

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 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 the West Nile virus, visit Larimer.org/westnile