Nearly three weeks after Thanksgiving, no dramatic post-holiday surge in COVID-19 has emerged in the latest state data, although some hopeful trends seemed to stall after the long weekend.
“We haven’t seen something significant to talk about now,” the state’s health director, Dr. Ngozi Ezike, told reporters Monday. “We’ll see for sure in this coming week. … We’ll keep our fingers crossed that maybe we’re not going to see a big bump.”
Before Thanksgiving, Ezike and other public health officials and medical experts urged residents to skip family gatherings, warning that the celebrations could become superspreader events. The virus that causes COVID-19 often hides in infectious people who aren’t showing symptoms, they noted, and it loves to spread indoors as unmasked people mingle closely — as they do over a holiday meal.
So some people stayed home for Thanksgiving 2020. Others celebrated with family, with varying attempts to be safe. And public health officials nervously waited to see the result.
With 21/2 weeks of data now in hand, the Illinois numbers offer a mixed picture, complicated by regional differences. For example, in the state’s north region — basically west of McHenry and Kane counties to the Iowa border — both COVID-19 case numbers and the positivity rate for COVID-19 testing have dropped by nearly half since mid-November. But so did the availability of intensive care beds.
Much of the rest of the country is arguably experiencing a post-holiday surge, based on COVID-19 hospitalization rates. Illinois and nearly all its neighbors are among the minority of states seeing a drop in hospitalization rates since Thanksgiving, although Illinois’ rate still places it in the worst third of states.
Here’s what the numbers tell us, so far:
Case counts
Looking only at confirmed COVID-19 infections, it would appear no evidence has emerged yet of a holiday surge in Illinois.
Because case figures can be erratic from one day to the next, researchers typically compute a seven-day rolling average — often averaging one day’s figures with those seen during the three days before and three days after. In Illinois, the seven-day average of new cases peaked a month ago, at more than 12,000.
As Illinois’ infection curve rose in the fall, the state imposed restrictions. The curve appeared to bend as the state continued tightening rules, culminating in a Tier 3 designation on Nov. 20 that limited capacity in some businesses and closed others where people could congregate, including indoor dining and bars except for outdoor service.
By Thanksgiving, the average had dropped to near 10,000 new cases and, after a brief rise, has since dropped below 9,000. That’s still significantly more than in the summer, which at one point saw an average of fewer than 600 new confirmed cases a day, but it’s a positive trend nonetheless.
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To compare different parts of the state, the Tribune calculated the number of new positive test results per 100,000 residents in each of the 11 regions established by the administration of Gov. J.B. Pritzker.
By this measure, all of the regions are generally trending better, including after Thanksgiving. Consider the west-central region, which covers most counties around Springfield and west to the Mississippi River. Its rate peaked above 150 cases per 100,000 people but has since dropped below 100 — still the highest rate of any region, but far lower than before.
Other trends appear more muddled. Chicago, for example, saw its rate fall after Thanksgiving, only to slightly increase the next week, leading Chicago’s health director to suggest the city was seeing a post-holiday surge. But only one Illinois region — the south, roughly from Mount Vernon to the state’s southern tip — saw an overall increase in its new case rate after the holiday.
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Public health officials and researchers have cautioned that new case counts alone can’t tell the whole story of the virus’s spread because the vast majority of infected people don’t get tested. So their cases are never recorded.
Also, around the holidays, the numbers may fluctuate based on when people choose to get tested and when labs can process the results.
Positivity rate
To try to account for the up-and-down nature of testing, government officials and researchers turn to another metric: the percentage of tests coming back positive, again based on a seven-day rolling average. The lower the rate, the better.
Here’s where the results are more upbeat, at least for regions outside the Chicago area. The rate drops that began in early to mid-November seemed to stall after Thanksgiving, but then resumed dropping in the past week. For example, the worst region in this group — the north — topped out near a 21% positivity rate, hovered near 15% in the week after Thanksgiving, and has since dropped to near 11%.
That’s still high. The World Health Organization recommends that the positivity rate should fall below 5% before loosening restrictions. Still, the north region’s rate has been halved within a month, with others also showing notable drops.
The data is less consistent for Chicago and the regions surrounding it.
In the city and three surrounding regions, the positivity rate started dropping in mid-November and flattened out after Thanksgiving at roughly 12% to 13%. Their rates have bobbed up and down since then.
The only Chicago-area region seeing a continued drop — both before and after Thanksgiving — is the one encompassing Will and Kankakee counties. It was once the worst in the Chicago area on this measure, but its positivity rate is now similar to that seen in the other Chicago-area regions.
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Hospitalizations
COVID-19 hospitalizations offer a relatively consistent way to monitor the spread of the virus, but this statistic also is known as a lagging indicator because it takes time for infected people to become sick enough to require hospital treatment.
In Illinois, hospitalizations peaked in most regions around Thanksgiving, reflecting trends seen with cases and positivity rates a week or so earlier.
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Nationally, Illinois is still one of the states with the highest hospitalization rates, near 40 hospitalized COVID-19 patients per 100,000 residents as of Monday, according to a Tribune analysis of data collected by the COVID Tracking Project. Neighboring Indiana and Missouri were higher yet, at 46 and 43 respectively.
But Illinois’ statewide hospitalization rate has dropped 16% since Thanksgiving. That’s consistent with declines seen across the upper middle part of the country, as the surge spreads south and to the coasts. Some states in those areas have seen rates roughly double since the holiday.
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One caveat with the Illinois numbers is that hospitals have become more choosy about who gets a bed, including sending some ER patients home with monitoring gear instead of admitting them.
The bigger concern has been whether the sickest of the sick patients — those needing intensive care — will overwhelm hospitals’ ICU wards.
Despite the overall decline in COVID-19 hospitalization rates, the seven-day rolling average of available ICU beds dropped in all of the state’s regions in November and remains low in most.
The state sets a threshold of concern at 20% availability, and the rolling average was below that in suburban Cook and in the region encompassing DuPage and Kane counties. Outside the Chicago area, ICU availability fell below 20% in four of six regions: north-central, west-central, Metro East and south.
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These numbers don’t show the situation on the ground level, from hospital to hospital. The Illinois Department of Public Health has declined to provide data on individual hospitals — and declined to explain why.
But the U.S. Department of Health and Human Services did release data for each hospital recently, showing wide disparities in how many virus patients hospitals have admitted and how full their ICUs have become.
Ultimately, public health officials and advocates have said, Illinois remains in a precarious spot — with more potential holiday gatherings around the corner that could quickly send the infection curve back up.
“We are starting to head in the right direction,” Ezike said in her address to the public Tuesday. “So many of you have sacrificed and employed all the public health mitigations, and I thank you, that that has gotten us to where we are. We still do have many more months to go, but let’s continue toward that light at the end of the tunnel.”
Chicago Tribune’s Dan Petrella contributed.
jmahr@chicagotribune.com
