Video: Arts correspondent Angel Idowu talks with music fans and artists about the event’s controversial return to Grant Park.

As thousands of music lovers flocked to Grant Park for the first day of Lollapalooza, a surge of confirmed cases of COVID-19 in Chicago and the suburbs prompted Gov. J.B. Pritzker to reimpose a mask mandate in state facilities for everyone, regardless of their vaccination status.

While Mayor Lori Lightfoot celebrated the return of the four-day music festival that is expected to draw more than 100,000 people to downtown Chicago each day, the Centers for Disease Control and Prevention added Cook County it its list of areas experiencing “substantial” transmission of the coronavirus.

Video: How are Loop businesses faring amid the pandemic? Watch our full interview with Kiana Distasi from the Chicago Loop Alliance.

Along with people in DuPage, McHenry and Will counties, everyone — regardless of vaccination status — in Cook County should wear masks indoors, according to federal guidance. Confirmed cases of COVID-19 are surging across the country because of the delta variant, and new data suggests the virus can now be spread by fully vaccinated people.

New mask rules will be released Friday by the Cook County Department of Public Health, officials said.

“The delta variant is the strongest version of COVID-19 yet and we must contain it through both vaccinations and prevention measures such as mask wearing indoors and in crowded outdoor settings,” said Dr. Rachel Rubin, the senior medical officer of the Cook County Department of Public Health. 

COVID-19 cases in Illinois have risen 80%, and officials expect the virus to continue to spread, according to a statement from the governor’s office.

“Vaccines are how we put this pandemic behind us for once and for all, but I will continue to evaluate the need for further additional mitigations,” Pritzker said.

Chicago is now recording an average of 192 cases per day, based on a seven-day rolling average, according to data from the Chicago Department of Public Health. In the past week, the number of cases has risen 64%, according to city data.

The city’s COVID-19 test positivity rate is now 3%, up from 1.8% during the past week, according to city data.

In addition, more than eight people have been hospitalized, on average, every day this week, up from an average of more than four people every day last week, according to city data.

Lightfoot on Thursday declined to renew her promise, made Monday in an interview with the New York Times, to reimpose a mask mandate on Chicagoans, regardless of their vaccination status, once the city passes the 200 cases per day benchmark set by local health officials. That would mean the city would meet the standard set by the CDC to deem an area where there is “substantial” transmission of the coronavirus.

Hospitalizations in Chicago are at the highest level since mid-June, according to city data.

However, Lightfoot said the data gives city officials “some reason for optimism, in quotes” because there are fewer seriously ill Chicagoans than in prevous months.

Chicagoans must get vaccinated as soon as possible to protect themselves from COVID-19, Lightfoot said.

“Without that protection, you are playing Russian roulette,” Lightfoot said.

Despite the surge, Lightfoot encouraged everyone at Lollapalooza to have fun and helped kick off the festival by introducing the Black Pumas to the stage by thanking visitors to Chicago for spending money in the city.

“Lollapalooza is the largest music festival in the world that is happening in 2021,” Lightfoot said. “It is a big deal.”

Video: Is Lollapalooza good for Chicago’s independent music venues? Watch our full interview with Chris Bauman from the Chicago Independent Venue League.

Contact Heather Cherone: @HeatherCherone | (773) 569-1863 | [email protected]