Mosquitoes collected in Carver County have tested positive for West Nile virus, the mosquito-borne bug that can cause fever and headaches and in some cases lead to encephalitis, a brain infection.

So far this summer, there have been no confirmed cases of Minnesotans coming down with West Nile illness, according to the Metropolitan Mosquito Control District.

District officials said Wednesday, however, that the virus had been found in a Carver County mosquito sample.

That isn't unusual for this time of year, ecologist Kirk Johnson said, but warm weather on the heels of the recent heavy rains could lead to more mosquitoes spreading the disease to birds.

"While people aren't necessarily at greater risk yet, we all should take common-sense precautions to avoid mosquito bites," Johnson said in a statement issued by the district.

The Mosquito Control District keeps track of reports of infected birds in an effort to reduce the risk of the virus, which is highest in mid- to late summer.

West Nile virus incidents rose significantly in Minnesota last summer after a four-year lull. Eighteen cases were reported by mid-August, with some victims requiring hospitalization, according to the Minnesota Department of Health.