State Department of Health officials are urging people to take precautions against West Nile Virus.
There are 18 confirmed cases of West Nile Virus in Minnesota this year, and 10 positive cases among blood donors. The total number of cases is up over previous years. Between 2008 and 2011 Minnesota had between two and 10 cases a year. No deaths have been reported.
The virus is commonly spread by infected mosquitoes. Officials recommend using mosquito repellent with DEET and wearing long sleeves and pants at dusk and dawn when mosquitos are most active.
Health Department epidemiologist Melissa Kemperman said West Nile can be dangerous.
"Fortunately, the majority of people infected with the virus will be asymptomatic and fight it off without even knowing that they had it," she said. "But about 20 percent of infected people will get quite ill from it."
Symptoms can range from an illness with a bad fever and headache to a central nervous system disease where the virus infects the brain or the lining of the brain, she said.
Kemperman said people in western Minnesota are at greatest risk for West Nile.
"The mosquito that carries this tends to breed in open agricultural areas so people in the western and southwestern part of that state are at greatest risk," she said. "That said, even here in the Minneapolis-St. Paul area we do have the mosquitos that carry it so there is some local risk as well."