With a rise in COVID-19 cases, Cook County was added Thursday to a growing list of Illinois counties where the Centers for Disease Control and Prevention recommends all residents wear masks in public indoor spaces, regardless of whether they’re vaccinated.

And with more than half of the state’s counties under that guidance, Gov. JB Pritzker also announced Thursday that he was mandating that anyone working in or visiting a state facility be required to wear a face covering, regardless of vaccination status.

Cook County as of Thursday showed an average case rate of more than 51 cases per 100,000 people, just putting it into the category of “substantial” transmission of the virus, according to the CDC’s new designations. The CDC established the new designations this week and the suggestion of indoor mask-wearing as the delta variant continues to spread across the U.S.

Cook joins DuPage, Will and McHenry counties as places where the cases are rising and the CDC recommends masking.

Pritzker on Thursday said with the rise in cases across the state, and the addition of so many counties to the CDC’s masking-recommended list, he was mandating that state facilities require masking, and said more requirements could follow if cases continue to rise. Pritzker said the CDC estimates that 80% of new cases are due to the delta variant, a highly transmissible strain of COVID-19.

When asked by telephone Thursday whether Cook County would adopt new masking mandates, County Board President Toni Preckwinkle demurred, responding that everyone at the press conference she was at was already masked.

“Well, you’re not in the room, but everyone is masked except when they’re speaking and we have a sign outside of our building that says masks are required within the building,” she said, before turning the question over to Cook County Health CEO Israel Rocha Jr.

“We will continue to work with the CDC and health partners to mitigate any information that we get and take the appropriate steps,” Rocha said. “Today’s decision from the CDC says when you’re [in] indoor environments, you should be masked, as we are today. And we will continue to be responsive to those steps.”

Cook County’s designation comes as Chicago itself is approaching an average of nearly 200 cases a day, according to city data, and as the city kicked off the return of the mega festival, Lollapalooza.

Mayor Lori Lightfoot on Thursday said she expected the city may hit 200 cases a day soon, but did not repeat an assertion she made to the New York Times earlier this week that such a number could portend a change in masking.

Lightfoot on Thursday said that there are other factors to consider, including hospitalizations, and noted that most of the new cases are tied to the delta variant and are among unvaccinated people.

Then, on Friday, the Chicago Department of Public Health released a statement acknowledging that Chicago had indeed surpassed 200 new COVID-19 cases a day. The agency recommended — but did not require — that everyone wear masks while in public indoor spaces. 

Cook County public health officials on Friday also recommended the same.