Those two critical metrics have put the county at "warning level" for potential action. And since the start of summer, the rate of infections has quadrupled.
At Edward Hospital in Naperville, there's been a 20 to 30% rise in cases in just the past week.
"Don't let your guard down. It's not over," urged Dr. Jonathan Pinsky, director of infection control at Edward Hospital. "There's still a lot of COVID. I know people are getting tired of wearing masks and tired of staying at home, but this is going to be a long haul."
Dr. Pinsky said that over the summer, most of the cases at the hospital involved young people who became infected at social gatherings. But now they're seeing more older patients.
"Part of it are younger family members who brought it home to them," Pinsky said.
Last week, there were 89 new cases for every 100,000 people in DuPage. That's up from 77 cases the week before, and well above the target of less than 50 cases, which is the recommended level for allowing students back in schools.
This week, students and parents staged rallies in Hinsdale and Wheaton calling for in-person instruction and fall sports.
"We have concerns," said Karen Ayala, executive director of the DuPage County Health Department. "We're not in full blown crisis in DuPage County in regards to COVID, but we are heading with several of our metrics in the wrong direction."
DuPage County is one of 30 Illinois counties now at "warning level." Another is DeKalb County, where Northern Illinois University is moving undergrad classes online for two weeks following a rise in cases fueled by parties.
"The young people then can transmit it on to the older people, and those are the ones who then get admitted to the hospital," Dr. Pinsky said.
Officials hope more mask wearing and social distancing will bring the numbers down and prevent the need for stricter measures in DuPage.