Mosquitoes have tested positive for West Nile Virus north of Chicago in Lake County.
The county Health Department says the mosquitoes were sampled Friday in the village of Mundelein. It's the first indicator of the disease's presence in Lake County this year. Last year, 14 sampled groups of mosquitoes tested positive, but there were no human cases.
Health Department Director Irene Pierce said Tuesday that hot weather typically increases mosquito activity.
The mosquitoes that carry West Nile virus, known as Culex mosquitoes, thrive in dry conditions.
Most people infected with the disease have no symptoms, but some may become ill up to two weeks after being bitten. In some people, especially the elderly, the virus can cause muscle weakness, inflammation of the brain, paralysis, coma or death.