The county announced the first reported human case of the virus this year in September. That case involved a Naperville man in his 50s.
West Nile virus is transmitted to people through the bites of infected mosquitoes. Approximately one in five people who are infected with the virus will develop symptoms including fevers, headaches, body aches, joint pains and vomiting. Less than one percent develop a serious neurologic illness.
Health department officials say residents should protect themselves against the virus by wearing insect repellant outdoors, and emptying standing water from items outside homes.