West Nile virus, previously confined to southern Utah, surfaced this week in mosquitoes along the Wasatch Front.
Mosquito abatement officials said a group of Culex pipien mosquitos in Utah County tested positive for the virus.
It's been a mild season this year with only one human case of the mosquito-borne illness in Utah. But the season doesn't end until the first hard freeze.
"We really don't want individuals to be complacent," said Bob Mower, Utah County's Mosquito Abatement director, in a prepared statement. "We haven't seen as many mosquitoes, but those that we have are of the species that carry West Nile."