The Iowa Department of Public Health has announced the first confirmed human case of West Nile virus in the state this year.

The health department said Friday that the case was a middle-aged woman in Clayton County who was not hospitalized.

Health officials say statewide surveillance has also found an increased number of mosquitoes infected with the virus. They're cautioning residents to get rid of mosquito breeding areas and to use insect repellent outdoors.

Dr. Patricia Quinlisk, the health department's medical director, says the West Nile virus season in Iowa typically lasts until the first frost.

Since West Nile first appeared in Iowa in 2002, it's been found in every county in humans, horses or birds.