In a building on the city's West Side, a hand-to-hand battle is being waged against a potentially fatal illness.
"West Nile virus, this is the season for it," said Dr. Bechara Choucair, Chicago Public Health commissioner. "And we want to make sure that we're doing the best to protect Chicagoans."
On Friday, ABC7 was given exclusive access to the Chicago Public Health Department's West Nile prevention lab. In the sterile environment, a small but determined group of scientists is able to assess the threat.
"We map everything out, and we're able to make a better decision and target our efforts," said Claudia Blanco, Chicago Public Health administrator.
It begins in the field where mosquitoes are gathered using traps that are filled with water and grass clippings. The insects are then refrigerated, which sedates them, before they're identified and sorted.
Specifically it's the Culex, called the northern house mosquito, which spreads the West Nile Virus from birds to humans.
"We had a mild spring. We had a hot and dry summer. And this is the perfect conditions for the northern house mosquito to breed and grow," said Dr. Choucair.
In fact, this summer has seen triple the usual number of Culex.
After the mosquitoes are ground up and their genetic material extracted, the samples are prepped and then analyzed by a machine, which can identify which mosquitoes are infected with West Nile and how infected they are.
Those samples can then be traced back to specific neighborhoods offering a map of where spraying is most needed.
"So we can base our decisions for spraying based on data and evidence rather than anecdotes," said Dr. Choucair.
Officials say their efforts are working. Earlier this month, one in four mosquitoes in Chicago were testing positive for West Nile. Officials now say that number is closer to one in 10.
The work in the lab, however, is far from done, with West Nile season likely to last until the first frost.
Chicago's West Nile lab was formed in 2003 after dozens of people died in Illinois in 2002.