That's why officials are urging people to mask up and avoid gatherings altogether if they are experiencing any COVID-19 symptoms.
Doctors also said an at-home test might not even detect the virus if symptoms are mild.
For now, Chicago officials are not requiring masks, but strongly recommend wearing them, especially in indoor spaces.
Chicago and suburban counties are now at "medium" community level, with more than 200 new cases per 100,000 reported in the last seven days.
As of today (5/6/22), Chicago's COVID community level is "medium" per the CDC. Because of this, we are now strongly recommending wearing a mask in public indoor settings.— CDPH | Chicago Department of Public Health (@ChiPublicHealth) May 6, 2022
Do your part to #ProtectChicago. Make sure you are up to date on vaccination: https://t.co/CaEaU8sAu7. pic.twitter.com/lWytPaEksk
"You want to be really careful," said Dr. Susan Bleasdale, director for infection prevention at UI Health. "If you're visiting your mother, and there's someone that is vulnerable, if you're going to visit them, you may choose to wear a mask the entire time you visit together."
If Chicago moves from medium to a "high" community level, more mitigations would be possible, but that would require a steep increase in hospitalizations, which have been on the rise but only moderately.
Illinois COVID cases
Illinois reported 7,709 new COVID cases and seven deaths Friday as the CDC said nine Chicago-area counties have reached a "medium" risk of transmission.
There have been at least 3,169,315 total COVID cases as of Friday, including at least 33,660 related deaths in the state since the pandemic began.
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As of Thursday night, 808 patients in Illinois were reported to be in the hospital with COVID-19. Of those, 66 patients were in the ICU, and 24 patients with COVID-19 were on ventilators.
A total of 22,018,536 vaccine doses have been administered in Illinois as of Thursday, and 64.76% of the state's population is fully vaccinated. The seven-day rolling average of vaccines administered daily is 14,163.
Cook, Lake, McHenry, Kane, DuPage, Will, DeKalb, Kendall and Winnebago counties have "medium" COVID risk levels, according to the CDC.
"You know, especially that 0 to 19 group, they're reporting the most cases every day," said Chris Hoff, with DuPage County Health Dept. "But we are seeing increases in every age group across the community."
In an email to Chicago Public Schools families and staff, CEO Pedro Martinez said the district would continue "strongly encouraging the use of masks in our schools, especially among our unvaccinated students, and especially when cases are rising." But the school system followed the city's lead in opting against a mandate.
"As we have done since the start of the pandemic, CPS will continue to follow the recommendations of the Chicago Department of Public Health when making decisions about how this change will impact our schools," Martinez wrote in the email.
The district has fought efforts over the past few months by a group of parents and a downstate candidate for attorney general to get rid of all COVID-19 precautions in schools. Martinez announced CPS would drop its mask mandate in March just a week after he had reaffirmed the school system's commitment to face coverings. Though his announcement cited a sharp decline in cases, he later hinted the move was intended to preemptively avoid a pending court ruling that would have blocked CPS' ability to mandate masks in the future. He assured families, though, that CPS would reinstate the requirement if cases rose again.
While masks still won't be required for now, the district will continue its isolation policy for unvaccinated students and staff, requiring those who are exposed to COVID-19 to work or learn from home for five days, then wear a mask in school for the next five days.
Sun-Times Media contributed to this report.