What is Driving the Rise in COVID Cases in Chicago? Data Points to One Age Group

COVID metrics in both Chicago and Illinois are beginning to show "signs of concern" as case numbers and positivity rates start to increase

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What's behind the latest rise in coronavirus cases in Chicago?

According to Chicago Department of Public Health Commissioner Dr. Allison Arwady, it appears one particular age group is seeing the largest increase in cases in recent days, a concerning trend reminiscent of last fall's surge.

"So the biggest thing driving this is increases in cases in our younger adults, and I want to highlight that," Arwady said during a press conference Tuesday. "Unfortunately, these sorts of increases are just what we were seeing in October as we were starting to see the beginnings of what became our huge surge. It was really the same case rates and younger adults that started this."

But could it have anything to do with vaccine eligibility?

According to Arwady, maybe.

"It is a sign that the vaccine efforts are working, but it is also a reminder for me, and hopefully for everybody, that there are people in the younger age groups I think who perhaps are being less cautious," Arwady said. "And whether that's because they're feeling confident that the older people they interact with are already hopefully fully vaccinated, or whether there's just a sense that COVID is over... so it doesn't surprise me to see that the cases are going up in the ages that are less eligible for the vaccine, but the patterns that we're seeing, to be very clear, are the same patterns, we were seeing in October as we were watching with some concern."

Coronavirus case counts in the city are starting to rise, with a current average of about 360 cases per day, compared to 292 one week earlier, according to the city's website.

"Sometimes people ask, isn't it just that you're doing more testing? No, because if it were just testing, we would see testing up 23% and cases up 23%. This is a true increase," Arwady said.

Of the more than 6,700 cases reported so far this month, more than 4,300 were in residents between the ages of 18 and 49, city data showed.

"It's been 18- to 29-year-olds, 30- to 39-year-olds, 40- to 49-year-olds at every point here in the outbreaks that have been the most predictive of seeing significant increases in cases," she said. "And so most of those folks have not been able to get a vaccine yet and I want to remind people, all people, but especially folks in those younger age groups who haven't been able to get a vaccine that we really need everybody to not stop doing the things that got us this far."

Arwady said that while the current case level remains in a moderate risk category, the rate of increase actually puts the city under a higher risk.

The positivity rate also climbed to 3.3% Wednesday, remaining in the low-risk category and far below the 30% high seen at the height of the pandemic, but marking an increase from a recent low of 2.7%.

While the trends so far mirror the lead-up to last fall's surge, it remains unclear if the current rise in cases and positivity signal a third potential surge.

"I don't know fully what's going to happen here," Arwady said. "I do know that we are pushing vaccine absolutely as quickly as we can, ramping up our monitoring for the variants we are seeing...and continuing to ask people to do what has gotten us this far. If we see a big increase in cases not accompanied by an increase in hospitalizations or deaths I don't worry about that as much. But if we start to see it impacting in serious ways, you know, and then the big question is what does this mean for reopening?"

Emerging variants of the coronavirus, believed to be more contagious, are also spreading across the city.

"We're seeing COVID variants spread in Chicago, and we are not testing every person who gets COVID for those variants, but we absolutely are seeing again that B.117 variant that first emerged in the U.K., that they're seeing a lot of in Michigan," she said. "We are also seeing more cases of it here in Chicago and we have seen some spread."

The increase, however, isn't unique to Chicago.

"They're actually worse in suburban Cook and the northeast, you know, the state overall," Arwady said. "Not an emergency yet, but these are... this is why we monitor these things and when we see signs of concern like this, it's a moment to watch and see what happens."

Her comments were echoed in part by Illinois Department of Public Health Director Dr. Ngozi Ezike, who said Tuesday that the state is "seeing some concerning plateaus and even increases in hospitalizations and cases."

“Even as we’re getting more and more vaccine doses, we cannot let our guard down, especially with these virulent new strains circulating,” Ezike said in a statement. “We’ve come so far and are so close to a more normal time, but we’re already seeing some concerning plateaus and even increases in hospitalizations and cases. We’re not out of the woods yet so continue to wear your masks, avoid large crowds, and keep six feet of distance.”

Health officials in Illinois on Wednesday reported 2,793 new coronavirus cases and 20 additional deaths, along with more than 107,000 vaccinations in the past 24 hours.

"I've been to this movie before and seen, you know, the rising positivity rates," Gov. J.B. Pritzker said Wednesday. "And I'm concerned about it and I've been saying all along, even as we have addressed the mitigations and tried to lower mitigations here or there, I've said we got to be careful about the variants. And I am concerned, I must tell you, you know, as I see numbers go up, is that the variants or is it a blip in the data? You know, what is it exactly? So we'll keep watching very closely, but I can tell you there is more activity going on and I think people maybe are being a little less careful, and I want to remind everybody please keep your distance, please continue to wear your mask, please be respectful of others."

Arwady said that while the city continues to make progress in vaccinating residents, she's particularly concerned about the short-term impacts of a surge, but remains optimistic for longer-term projections.

"I remain really confident that this summer, assuming we continue to see really good vaccine demand and really good uptake as vaccine supply increases, we'll be in good shape this summer, but I am really worried about this next sort of four to eight weeks," she said.

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