Charles Rex Arbogast/Associated Press
The Illinois National Guard operates a COVID-19 drive-thru test site for medical personnel and first responders at a closed vehicle emissions testing center in Chicago in March.
Charles Rex Arbogast/Associated Press
Illinois' declining number of positive COVID-19 cases has started flattening over the past week in some areas of the state, while other areas are starting to see a slight uptick, according to two epidemiologists in Chicago.
"Though it's still tentative ... the slowdown has really stopped, and we're getting a little bit more of a flattening potentially, and a bit of an uptick," said Sarah Cobey, an epidemiologist at the University of Chicago.
The number of new positive cases in Illinois has increased for three days in a row, with 869 new confirmed cases reported by the Illinois Department of Public Health Thursday, which is higher than the 7-day rolling average of 778 new cases. But the state's seven day case positivity rate has remained flat, between 2 and 3% over the past month, compared to 14% in mid-May.
IDPH data show younger people are increasingly accounting for more positive cases. As of June 30, 16.6% of positive cases were patients in their 20s and patients in their 30s represent 16.5%, compared with 14% of people over 70. Still, people over 70 years old represent more than two-thirds of the deaths from COVID-19 in the state. (See more about the state's numbers here and here in a WBEZ/The Chicago Reporter collaboration.)
While Chicago Mayor Lori Lightfoot on Wednesday said she believed the city's COVID-19 caseload continued to be on the decline, a day later she announced that anyone coming from states where cases are surging would be ordered to quarantine for two weeks, starting Monday.
Cobey works closely with Jaline Gerardin, an epidemiologist at Northwestern University. Both women have advised the state on COVID-19 data collection and forecasting since the start of the pandemic.
"The trend we've seen over the last few days is not cause [for] unconcern," Gerardin said. "Some places may be starting to rise and some places on the downslope are flattening out and some places are continuing to go down. It's a mix of things."
Geradin and Cobey say much more information is needed to better understand the data collected and truly assess how the state is handling the spread of COVID-19.
Here are other issues the epidemiologists noted about the state's current COVID-19 situation:
Test turnaround time is slow — and that means reported data is lagging
While some testing sites can provide results in 24 hours, others are still taking up to a week, Cobey said. Plus, people often come in for tests a few days after symptoms start, which means a person is considered a confirmed case a week after they were likely infected.
All of this means the daily reported numbers this week are really reflecting the reality from a few weeks ago, before Illinois reopened bars and restaurants in the shift to Phase 4.
"It's way too soon for restaurants and bars to be driving that," said Gerardin of the current numbers. They expect shifting to Phase 4 will only result in higher numbers of positive cases statewide.
Cobey says she and Gerardin recommended testing sites across Illinois also start tracking the date people start noticing COVID-19 symptoms.
Hospitalizations and ICU bed numbers are better indicators than daily positivity rates
Cobey says it's important to look beyond the number of new positive cases to evaluate how well states are combating the virus. In fact, most modelers in Illinois don't base their forecasts on positive case trends.
"What we look toward more often are hospital admissions, admissions to the ICU and of course deaths," Cobey said, even though those numbers can also lag. "Though deaths are such a lagging indicator we wouldn't expect them to provide a first signal."
The number of hospital beds with COVID-19 patients has flattened over the past week, but an analysis provided by Gerardin shows certain areas of the state are seeing upticks in COVID-19 patients in the hospital and the ICU, especially in the Northeast and North Central region of the state.
She is especially concerned about hospitalization and ICU rates in the southern part of Cook County, and Will, Grundy and Kankakee Counties.
We don't know who is being tested and how often
The Illinois Department of Public Health said positivity rates have remained flat while we're seen an increase in new positive cases. A spokesperson credited that to increased testing, not an increase in infections.
Illinois has tested an average of 29,000 people per day in the past week, which is much higher than average testing rates during the peak of the pandemic. But Cobey and Gerardin said more data is needed to understand who is included in those increased testing numbers.
"Say they are testing the baseball team every single day," said Gerardin. "That's going to be leading you a different direction versus this is all people coming to the ER with symptoms. So there's definitely a level of deeper understanding that's needed."
The Illinois Department of Public Health did not immediately respond to a request for more information about who is being tested in the state.
Early warning data tracking still slowly ramping up
Cobey and Gerardin have pushed for the state to implement a "sentinel surveillance system" to help understand change in case trends as quickly as possible.
"We don't really have the best set up right now to detect these changes in transmission as soon as they happen," Cobey said. "We're seeing something that's sort of lagged and kind of blurred."
Under this system, testing sites would specifically track a certain subset of patients who come in for testing with COVID-19 symptoms. Those patients would be flagged and asked additional survey questions to create a consistent set of samples and help the state immediately assess trends.
"We don't necessarily need to know the exact numbers across everyone in Illinois," said Gerardin. "We can look at easy access groups to assess the trend."
According to both epidemiologists, two outpatient clinics have started using this early warning tracking system. Plus, all hospitals will start automatically testing women coming in to give birth, which is a group that can be consistently tracked and are less affected by changes in COVID testing statewide. Other states already test this population to do similar tracking of COVID cases.
IDPH did not immediately return a request for more information on this program and where the first two testing sites are located.
Kate McGee is a reporter at WBEZ. Follow her @McGeeReports.