A Delta County resident has tested positive for West Nile virus, the state said Friday afternoon, confirming Colorado’s first confirmed human case of the disease this year.

The first case arrived unseasonably late in Colorado; previous state data indicates infections often begin in the spring. The virus had previously been detected here this year: Mosquitoes carrying the virus have been identified in Boulder, Larimer and Weld counties.

The condition of the Delta County resident is unknown. A spokesman for the state Department of Public Health and Environment declined to release further information, citing patient privacy.

“This disease is spread primarily by mosquito bites,” Natalie Marzec, the manager of the state health department’s zoonotic disease unit, said in a statement. “Coloradans can protect themselves by using effective insect repellent, wearing protective clothing that minimizes exposed skin, or staying indoors when mosquitoes are active.”

In 2021, Colorado reported 175 human cases of West Nile and 11 deaths, the health department said. Most people who contract the virus have no symptoms; one in five will have flu-like symptoms. Fewer than 1% of those infected develop a serious, and potentially fatal, form of the illness, the state said.