The first cases of West Nile virus this year in north suburban Glenview were reported Wednesday, the Pioneer Press is reporting.
The North Shore Mosquito Abatement District stated two findings were discovered July 8, both testing positive for the virus.
Dave Zazra, district communications manager, said three human cases occurred in 2012, but no one sickened.
Dr. Steve Schrantz, an infectious control physician for NorthShore University HealthSystem, said common West Nile virus symptoms were head and muscle aches and fever.
"But 80 percent of the people infected show no signs because their antibodies deal with it," he said.
By mid-summer, West Nile is usually found in birds and mosquitoes, and human cases begin to occur in late August and early September, he said.
"Every season is different. We all thought there would be less West Nile because of immunity. Last year was one of the worst since the first outbreaks in the early 2000s," Schrantz added.
Zazra said the district regularly does not disclose the locations of confirmed cases because people would know where the mosquito traps were set.
"You should just assume if a mosquito lands on you, it could be West Nile. It would be a big mistake if you knew where the cases were found," he said.
He also said this year's insect crop were known as "nuisance flood water mosquitoes," borne of recent heavy rains in forest preserves districts and heavily wooded areas.
"Flood water mosquitoes are not known to carry West Nile. The quality of life is less because they're aggressive."