Salt Lake County has confirmed its first human case of West Nile virus in 2026. Cottonwood Heights issued a public health advisory Wednesday, Sept. 9, urging residents to take protective steps as mosquito season continues.

Mosquitoes across Salt Lake County, including areas serving Cottonwood Heights and Holladay, have tested positive for the virus, according to the advisory posted on the city's website. The Salt Lake County Health Department said mosquitoes can travel several miles, meaning residents countywide face risk regardless of where the confirmed case occurred.

The county has not identified the patient. Neither location nor severity of the illness has been disclosed.

The pattern extends across northern Utah. KSL reported that four people in Davis County had been hospitalized with the neuroinvasive form of West Nile virus as of Sept. 4. Davis County Health Department Epidemiologist Sarah Willardson confirmed those hospitalizations and said about one in 150 infected people develop the severe neuroinvasive form.

"Really, anybody can become infected with the neuroinvasive form. But it is more likely to be an individual who's older, like those that are 65 years of age and older, or people who have an immunosuppressed condition," Willardson told KSL on Sept. 4.

Utah County also confirmed its first human case around Tuesday, Sept. 1, with that patient developing neuroinvasive disease, according to the American Fork Citizen.

Most people infected with West Nile virus show no symptoms, the Cottonwood Heights advisory states. Those who do get sick may develop fever, headache and body aches. Adults over 50 and people with weakened immune systems face higher risk of serious illness.

The city's advisory lists specific steps residents should take:

  • Use EPA-registered repellents containing DEET, picaridin, IR3535 or eucalyptus oil.
  • Wear long sleeves and pants when outdoors after dusk.
  • Drain standing water from buckets, flowerpot trays, pet dishes, toys and old tires.
  • Keep gutters clear of debris.
  • Check window and door screens for holes.
  • Trim weeds and tall grass where mosquitoes rest during the day.

Mosquito season in Salt Lake County continues until the first hard freeze. The Salt Lake County Health Department has not announced a timeline for its next public update on West Nile activity.