First case of West Nile virus confirmed in Larimer County, second under investigation

Ravyn Cullor

The first case of human West Nile fever in Larimer County this year has been confirmed in an unidentified Fort Collins resident. At this time, a second case is being investigated, according to a news release by the Larimer County Department of Health and Environment.

West Nile virus occurs after being bitten by an infected Culex mosquito, with around 25 percent of those infected coming down with West Nile fever. One percent of those who show symptoms will develop critical illness, chronic disability or even death, according to the release.


Mosquitoes are trapped in Larimer County to test for the virus starting in June each year, which did uncover infected individuals earlier this summer.

According to a previous release, a variety of mosquito called Culex mosquitos tested positive in Larimer County with a vector index of 0.004. The vector index is the approximate proportion of mosquitoes trapped per night which are infected with West Nile virus, according to the Center for Disease Control.

The county health department works with cities, Vector Disease Control International and experts at CSU to monitor and assess the risk to citizens.

West Nile virus is preventable both by county action, like deploying larvicide, and personal action, according to the release.

The health department recommends following the four D’s to protect one’s self from West Nile virus:

  1. Defend against bites by using an effective insect repellent like DEET, Picaridin, Oil of Lemon Eucalyptus and IR3535.
  2. Avoid being outdoors between dusk and dawn, which is the Culex mosquitoes peak feeding hours.
  3. Dress in long sleeves and pants to minimize biteable skin surface.
  4. Drain standing water on in yards and gardens which serve as breeding areas for the mosquito.

For more tips and information about West Nile virus in Larimer County, the county Department of Health and Environment recommends visiting

Collegian reporter Ravyn Cullor can be reached at or on Twitter @RCullor99.