The new recommendation comes as CDC data shows "substantial" COVID-19 transmission. County and state health officials looking at an uptick in case numbers they haven't seen in months.
ABC 7 Chicago was granted access inside the Rush University Medical Center lab tracking the delta variant's prolific rise in the city.
"We went from under less than 10% of our surveillance specimens being delta to 80% plus," said Dr. Stefan Green, PhD., director of the Genomics & Microbiome Core Facility at Rush University Medical Center.
"Over the last 7 days, our daily average has been about 51-52 people per 100,000 people. And according to the CDC's guidelines, this outs us (Cook County) in a significant community spread of COVID-19," said Dr. Rachel Rubin, senior medical officer at Cook County Dept. of Public Health. "Everybody, whether you're vaccinated or not, should be masked indoors-in public places."
WATCH: Cook Co. announces 'universal' mask guidance for indoors
At The Book Table in Oak Park, they have been operating by the book when it comes to masking recommendations for customers, but the new guidance from Cook County health officials has the owner feeling like she's now in a bind.
"I'm frustrated by the whole thing because I think the recommendation is not enough," said Rachel Weaver, co-owner of The Book Table.
Weaver said she'll change her sign to ask all customers to wear masks now, however, enforcing it is a whole other matter.
"At this point, it's just gotten too difficult, so I just don't think it's fair to have to make the staff enforce it," Weaver said.
Following guidance from the CDC, based on our current local COVID-19 data, we're now recommending that everyone over 2 years old, regardless of vaccination status, wear masks in public indoor settings. Masking outdoors remains optional, where the risk of transmission is lower. pic.twitter.com/IuNcT9Wqew— ChiPublicHealth (@ChiPublicHealth) July 30, 2021
But there are mixed opinions.
"We're hoping that this is as far as it goes. We definitely don't want to see a mandate," said Sam Sanchez, chair of the Illinois Restaurant Association.
North Side bar Delilah's temporarily closed due to COVID Friday evening. The owner wrote on Facebook: "We have had a few positive test results among our fully vaccinated staff and we have decided to close for a couple of days out of an abundance of caution."
In Humboldt Park, Dinah Grossman, owner of Spinning J Bakery and Soda Fountain, is closing the dining room and returning to take-out only.
"We wanted to protect our crew, our small crew of about a dozen people, and we wanted to protect our patrons who come in, and a lot of those are kids who are not vaccinated," Grossman said.
WATCH | Mask recommendations put businesses in a bind, some say
The new recommendation from Cook County Department of Public Health is that everyone wears a mask indoors in public places like bars, restaurants and retail stores -- regardless of vaccination status. The same recommendation applies in outdoor situations with crowded conditions.
"So when we say that you need to have masks indoors, even it's it's not stamped into law, this is what's considered best public health practice to keep us all safe," Dr. Rubin said.
Based on the latest advice from the Chicago Department of Public Health, Lollapalooza will require masks in any indoor spaces at Grant Park beginning Saturday. We encourage all fans attending the festival to bring a mask as they attend the final two days of the festival. pic.twitter.com/EHndLVR55i— Lollapalooza (@lollapalooza) July 30, 2021
While Lollapalooza is the purview of the City of Chicago, the county's top health official encouraging masks there, too.
Starting Saturday, Lollapalooza will mandate masks in all indoor spaces at Grant Park, regardless of vaccination status. The music festival is almost completely outdoors, but there are some indoor spaces, like the merchandise store, two hospitality lounges, and the box office. The new policy follows the city's latest guidance.
"If you're in this large congregate setting where there are a lot of people very close together, you could also be prudent to put on a mask -- even at Lollapalooza, even if you're vaccinated. But the hope is that it will not become a super-spreader event," Dr. Rubin said.
Dr. Rubin said she hopes that people and businesses will voluntarily comply with the new masking recommendation, which was prompted by the surge in COVID cases driven by the Delta variant, which is twice as contagious.
"To me, it makes it even easier to just say, 'Hey, this is our rules now, this is what we're doing, everybody that comes into this establishment needs to have a mask,'" Dr. Rubin said.
But with pandemic and mask fatigue a reality, that might be easier said than done.
"It's tough, it's just a really tough situation right now," said Cindy Fellencer, co-owner of Kribi Coffee.
"I'm happy with it," said Kearson Roberts, who supports the mask recommendation. "I think that it's something we need to protect each other, we need to protect our economy and we want to keep this economy open and to be able to have things like concerts and festivals."
Cook, DeKalb, Grundy, Kendall, LaSalle and Boone counties have now joined the list of Illinois counties showing "substantial" community transmission of COVID-19. DuPage, McHenry and Will counties are also at the "substantial" risk level.
"As public health officials, we are extremely, extremely concerned about this rise," Dr. Rubin added.
"It's time for caution," said Steve Brandy, public information officer for Will County Health Dept. "That is a reminder that we are far from done here, and the fact that about 80% of these new cases in Will County are connected to the delta variant."
In Indiana, Newton and Jasper counties are at "high" rates of transmission. Racine County in Wisconsin is at the "substantial" level.
This delta variant is probably in the range of two to three times more contagious than the original strain of the virus, and we have to be mindful of that," said Dr. Robert Citronberg with Advocate Aurora Health.
But many doctors saying the only way to slow the uptick down is to get more people vaccinated.
"The delta variant is more contagious but it's been allowed to spread because we haven't had enough people vaccinated, which is now why you're seeing employers or businesses, mandating vaccine because that's the only way to stop the spread of this virus, and by the way, other variants that might emerge, down the line."
The new CDC guidelines recommend everyone in those counties start wearing masks indoors again, even if they're vaccinated.
CDC COVID-19 Transmission Levels by U.S. County
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"Honestly it makes sense, even though it kind of sucks, but I'd rather do that than like another shutdown," said Kelly O'Brien.
County health officials say the only way to slow this uptick down is to get more people vaccinated.
"The only thing this virus cares about is surviving ...to really take advantage of people who aren't vaccinated," said DuPage County Health Dept. Executive Director Karen Ayala.
Chicago's top doctor believes the city will also be moving into the "substantial" risk category very soon.
"I would expect that as we watch this over these next few days, you know," Dr. Allison Arwady said. "I wouldn't be surprised if by, you know, early next week we're making some formal announcements. This is related to the delta variant, and the fact that it is here, and it is spreading."
Right now, Chicago is seeing an average of 190 new cases per day and that number keeps inching higher.