Mosquitos captured in two different areas of Weld County have tested positive for West Nile virus, county officials said Thursday.
Health officials monitor mosquito traps in three parts of the county — zone one, including Greeley, Evans, Kersey and LaSalle; zone two, including Johnstown, Milliken and Platteville; and zone three, including Firestone, Dacono and Fort Lupton.
According to a news release from Weld County, mosquitos trapped in zones two and three have tested positive for West Nile. Currently, there are no human cases of the virus in Weld County.
“The increasing hot weather often leads to favorable conditions for the Culex mosquito that carries West Nile virus,” Weld County Health Department spokesperson Jason Chessher said in the release. “The public needs to be vigilant because West Nile Virus has a permanent summer presence in Colorado.”
Last year was Colorado’s worst West Nile virus season since 2003, when the virus arrived in the state. The state had 634 known cases in more than half of the state’s counties — 51 of those people died and 386 were hospitalized.
Arapahoe County reported the first known human case of West Nile virus in Colorado for 2024 in June, marking an early start to the mosquito-borne disease season. Typically, Colorado doesn’t see its first West Nile cases until July, and they take off in August.
To prevent infection with West Nile virus county health officials and the Centers for Disease Control and Prevention recommend:
- Wearing insect repellant with DEET or another ingredient approved by the Environmental Protection Agency during outdoor activities
- Avoiding spending time outdoors around dawn and dusk, when mosquitoes are most active
- Using mosquito netting when camping
- Avoiding stagnant water sources, such as ponds, and checking around your home to regularly drain standing water
- Wearing long-sleeved shirts and long pants for outdoor activities and treating clothes with permethrin
- Draining flowerpots, tires and other items that collect water, which mosquitoes use to breed
- Keeping window screens in good repair
Most people who have the virus don’t get sick, making West Nile difficult to track.
Only 20% of people bitten by mosquitoes carrying the virus will develop symptoms — including fever, headaches, body aches, skin rashes and swollen lymph glands, according to the CDC.
While most people infected with the virus don’t get sick, symptoms for those who do appear between two days and two weeks after infection, CDC officials said.
About one in 150 people who are infected develop a severe illness or life-threatening symptoms, including high fevers, tremors and convulsions, muscle weakness, paralysis and inflammation of the brain and spinal cord.
Less than 1% of people with West Nile cases die, according to the CDC.
Sign up for our weekly newsletter to get health news sent straight to your inbox.