A Utah County resident has been diagnosed with the first confirmed human case of West Nile virus in the county this season.

The Utah County Health Department announced the case on Monday, Aug. 31, saying it involves neuroinvasive disease, the most serious form of the illness. Neuroinvasive West Nile virus (WNV) can cause meningitis, encephalitis or acute flaccid myelitis and may require hospitalization. Less than 1% of people infected with WNV develop it.

The department is urging residents across Utah County, including Alpine, Highland, Cedar Hills and Lehi, to take precautions against mosquito bites.

The department and Utah County Mosquito Abatement are reviewing surveillance data and conducting additional assessment in the area where the case was identified.

"This case is an important reminder that West Nile virus is present in our community and can cause serious illness," said Aislynn Tolman-Hill, the department's media contact.

The case comes during a year of elevated mosquito activity statewide. As of Aug. 22, Utah had recorded 15 human West Nile cases in 2026, compared with one at the same point in 2024 and six in 2025, ABC4 reported. The share of tested mosquito pools statewide that came back positive stood at 12.3%, up sharply from 2.4% in 2024 and 3% in 2025.

Those statewide figures predate the Utah County case by nine days, so the county's case may not be reflected in the totals.

What residents should know

Most people infected with West Nile virus do not develop symptoms, according to the health department. About one in five develop fever, headache, body aches, joint pain, vomiting, diarrhea or rash. Warning signs of the more severe neuroinvasive form include high fever, severe headache, neck stiffness, confusion, seizures, tremors and muscle weakness.

Mosquitoes that carry the virus are most active at dawn and dusk. The health department recommends:

• Using insect repellent containing DEET, picaridin or oil of lemon eucalyptus, especially at dawn and dusk
• Wearing long sleeves and pants when possible
• Checking that window and door screens are intact
• Removing standing water around homes

Residents who notice heavy mosquito activity or standing water they cannot eliminate can file a service request through Utah County Mosquito Abatement on the health department's website. Current trap counts, spray schedules and treatment maps are also posted there.