Illinois just announced a record number of new COVID-19 cases. Positivity rates for coronavirus testing are up too. So are hospitalizations and deaths.
But a deeper look at the data can soften the sense of alarm somewhat — at least for the Chicago area, where many pandemic metrics have remained steady for months until some recent upticks. And the state as a whole is still in better shape than its neighbors on most of those same statistics.
As a pandemic-weary public braces for winter, the latest Illinois figures have prompted researchers and public health officials to offer a mix of warnings and reassurance. They worry a second surge may be starting in Illinois while also noting that the shifting pandemic threatens some areas more than others.
“Chicago is doing a little better than downstate Illinois, Illinois is doing a little better than Wisconsin, etc. But broadly, COVID is not going well,” Chicago’s public health commissioner, Dr. Allison Arwady, said in a Facebook Live session on Thursday.
Gov. J.B. Pritzker on Friday told reporters he was deeply concerned about a “new wave” of infections. Earlier in the week, he implored residents to wear masks and avoid close contact with others.
“To date, Illinois has had relative success keeping this virus at bay,” Pritzker said Wednesday, “and we’re still doing better than many of our neighbors. But we can’t let up.”
At the same time, researchers caution that — even seven months into the pandemic — its trajectory remains hard to predict. Without frequent, random testing to gauge the virus’s true spread, the public is left with a buffet of data options that have various quirks and can be tricky to interpret.
Here are the figures researchers cite most often, how the Chicago area measures vs. other parts of Illinois, and reasons for concern as fall moves into winter:
Case counts are rising, but …
Researchers and public health officials agree there’s reason to be nervous in the greater Chicago region. Look no further than the count of new COVID-19 cases reported each day.
The Chicago region — defined by the state as Cook, DuPage, Kane, Kankakee, Lake, McHenry and Will counties — peaked this spring at roughly 2,350 reported cases per day, based on a seven-day rolling average.
After “bending the curve,” that average fell below 500. Then cases began increasing slowly this summer. That growth eased a bit in September but took a sharper turn higher this month. The latest case figures have averaged more than 1,800 daily.
In other words, we saw a dramatic drop in cases, only to see much of that improvement wiped out.
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There are caveats. To start with, assume more people have been infected than these numbers show, as some people never develop symptoms and many don’t get tested. In Chicago, according to Arwady, roughly 3% of residents have officially tested positive during the pandemic, but she suspects 15%-20% actually had the virus at some point.
Perhaps more importantly to interpreting trends, far more people are being tested now than in the spring, when testing supplies were scarce. So it’s difficult to tell how many of the growing case numbers are part of bigger outbreaks, and how many are the result of increased testing detecting more cases.
That’s where another metric comes into play: the positivity rate, which is the number of confirmed new cases divided by the number of tests given. This statistic has been tracked consistently since May, and it offers a less alarming assessment of the Chicago region. The positivity rate was largely flat since late June before ticking above 5% this month. But that’s still below the 8% threshold of concern set by the state.
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Still, taken as a whole, the figures are concerning, particularly in the past week, Arwady said. In the city of Chicago, she said, a boost in testing alone can’t explain the rise in cases, which has been seen in all races and ethnicities, in all age groups and across the city.
“We are seeing real increases here,” she said.
Other indicators: Little movement
Hospitalizations are a steadier barometer of the pandemic impact than case numbers, because sick people tended to go to the hospital even when testing was limited. But researchers caution that hospitalization figures can lag a couple of weeks behind infection trends, because it can take people a while to get sick enough to be hospitalized.
Still, the admissions figures for the Chicago area appear to have followed a trajectory similar to the positivity rate — with some relatively small ups and downs, including an uptick this month.
With that uptick, the entire region was seeing about 100 new hospitalizations a day for COVID-19-like symptoms in early October, roughly a fourth of the numbers seen during the first wave’s peak.
One caveat: The data is based on symptoms similar to those caused by COVID-19 — not on actual testing. So it is not possible to discern from these figures exactly how many of the patients were infected; about 25 people a day were typically admitted for such symptoms well before the pandemic began.
In addition, younger people now account for a larger number of cases, and this group is less likely, in general, to require hospitalization. That means the latest hospital figures may not track as closely with the pandemic’s spread.
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Another lagging indicator is the most grim: deaths directly tied to COVID-19. While this figure doesn’t include other so-called excess deaths likely related to the pandemic, researchers say the death count still offers one of the best indications of the pandemic’s toll.
In the Chicago area, the trend line for deaths has also been relatively flat in recent months. Even with a slight rise in October, deaths remain an eighth of what they were at the peak of the first wave.
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Overall, most indicators have been relatively flat for the region since early summer, but with increases this month that offer an early warning sign of potential trouble ahead.
The same can’t be said for much of the rest of Illinois.
“In the other regions this is absolutely not the case,” said Jaline Gerardin, a Northwestern University assistant professor of preventive medicine who works with the state on virus modeling.
“They’ve had a substantial second wave, about as large or larger than their first and in some regions still on the upswing,” she said.
The pandemic’s rural phase
When looking at raw numbers, the Chicago area remains the epicenter of the pandemic in Illinois. But that’s because of the lopsided way people are crowded into the northeast corner of the state, which holds roughly two-thirds of all Illinoisans.
The pandemic looks far different when looking at infection rates, a metric that adjusts for the population differences.
Early in the pandemic, state officials split Illinois into four regions for tracking purposes. The Northeast region, which includes Chicago and its suburbs, initially had the highest rate, topping 27 cases per 100,000 people this spring. Then the region saw a dramatic drop, while other regions’ rates began climbing.
By early July, the infection rate in the South region surpassed that of the Northeast. A month later, the Central region followed suit, and the North Central region joined them a couple of weeks after that.
Now two of the four regions — North Central and Central — have rates topping 30 cases per 100,000 residents. That’s higher than the rate ever was in the Northeast region, even at the pandemic’s peak.
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On other metrics — death rate, positivity rate and hospital admissions — the northeastern part of the state now has either the lowest or second-lowest rates of the four regions.
The difference in death rates is stark. Though all of the numbers are small, less than one death per day per 100,000 residents, the NorthCentral region’s death rate is twice that of the Northeast region. For the Central and South regions, it’s triple.
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Even looking at raw case numbers, the regional trends are apparent.
Take two dates when Illinois set records for the most confirmed cases. The first was on May 12, in the thick of the first wave, when the state announced 4,014 new cases. Nearly 90% of those cases came from northeastern Illinois.
On Friday, when the state announced a new record of 4,554 new cases, northeastern Illinois accounted for 61% of those cases — less than the 68% of the state’s residents who live there.
Stephen Kissler, a Harvard University researcher who studies mathematical models that measure disease spread, said the virus has trickled out of the country’s major population hubs into other areas.
“Many of the communities that are getting hit now are not the ones that were hit earlier in the spring,” he told reporters in a conference call Wednesday.
And he said that, even with some limited immunity potentially developing in early hot spots, “in all but the very hardest hit communities in the country, there’s still plenty of susceptible people around to sustain further outbreaks coming into the fall and winter.”
Despite the growing numbers seen in Illinois, a Harvard University dashboard still ranks the state’s risk of resurgence in the nation’s middle tier, ranking Illinois 17th this week based on the rate of new cases.
It can be difficult to compare states’ positivity rates because of how differently numbers are reported. But in looking at other metrics compiled by The COVID Tracking Project, Illinois had the 18th highest weekly average of hospitalized COVID patients and the 21st highest weekly death rate.
Notably, of the five states that border Illinois, all have higher hospitalization rates and all but one have higher death rates. In Wisconsin, for example, hospital admission rates are double those seen in Illinois.
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Worry ahead?
Public health officials and researchers caution that a lot of unknowns remain that could lead to spikes in cases. Among them:
* Cold weather: Viruses tend to like it, or rather the drier air that comes with it. Plus the weather forces people indoors, where there’s no breeze to dissipate the airborne virus. The coronavirus family of infections, which birthed COVID-19, tends to peak in December or January, but Kissler said it could be a couple of months earlier with COVID-19, in part because so many people have yet to be exposed.
* Schools: Early national numbers indicate schools haven’t sparked the number of outbreaks some experts feared, Kissler said. But with more schools returning to in-person learning, that could change. Illinois won’t release names of districts that have seen outbreaks, making it difficult for the public to track.
* Shifting demographics: Case trends suggest that more younger people are now getting infected. That group is less likely to get really sick from the virus — a good thing — but the age shift could make it harder to identify outbreaks before they infect more vulnerable people.
* The holidays: November and December traditionally bring people together, with many college students coming home and extended families intermingling. This can fuel the spread of disease, although the pandemic is expected to reduce the number and extent of gatherings.
* Pandemic fatigue: The vast majority of people remain susceptible to the virus, with a vaccine not expected for wide distribution until mid-2021. People may grow tired of wearing masks and socially distancing, and politically charged debates over those precautions don’t help.
And so the message for Chicago-area residents — as frustrating as it can be for some — is similar to what it’s been for months: We’re not as bad off as we once were. Masks and distancing have helped a lot. But the virus continues to linger. And signs point to more spread. So be careful and vigilant.
“The bottom line is … I think people are getting COVID fatigue,” Arwady said. “I think this is real, that people are feeling like they are tired of wearing their masks and they are tired of social distancing.
“The problem is if people let up on this — (if) they get COVID fatigue — that starts to slip just a little bit, and we see cases potentially really shoot up.”
jmahr@chicagotribune.com
