One of Illinois’ most familiar COVID-19 barometers is going away.
The state Department of Public Health announced Tuesday it will no longer report seven-day average case positivity rates — figures that, since the early days of the pandemic, had offered a quick glance at how rampantly the virus was spreading at any given time in different regions or across Illinois as a whole.
The change in coronavirus data reporting follows new guidelines set by the U.S. Centers for Disease Control and Prevention, which place more emphasis on hospitalizations and case rates per 100,000 residents.
With vaccinations and at-home testing more accessible, experts say those numbers provide a better idea of the virus’ trajectory.
Positivity rates, which compare the number of positive tests confirmed to the total number of tests performed, are “outdated” at this point of the pandemic, according to acting Illinois Public Health Director Dr. Amaal Tokars.
“Test and case positivity rates were seen as a good way to monitor the level of community spread early in the pandemic. At this stage, now that we have vaccines and effective therapies available, it is more useful to rely on data that indicates the case rate, disease severity and the level of strain on [the] health care system to guide our public health recommendations,” Tokars said.
The updated CDC guidance means states don’t have to tally all negative antigen tests for public health officials, so the state can’t calculate positivity rates either way.
Instead, the Department of Public Health is highlighting county-by-county CDC metrics that were rolled out earlier this year with indoor masking guidelines: the number of new COVID cases detected per 100,000 residents over the past seven days; the number of new COVID hospital admissions per 100,000 residents for the past week; and the percent of in-patient hospital beds occupied by COVID patients.
Those figures are considered low in 98 of 102 Illinois counties — including the entire Chicago area — meaning most people don’t need to wear masks in public indoor places.
But four southern Illinois counties — Pope, Gallatin, Saline and Hardin — have hit the “high transmission” level, as cases have been slowly rising statewide for about three weeks.
“It is happening in a context of cases that are overall much lower than we saw in the winter, but [we’re] still seeing a steady increase now,” Tokars said.
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The average statewide case rate has risen from a rate last week of about 10 infected residents per 100,000, up to a rate of about 14 per 100,000. That figure topped 250 at the height of the Omicron variant surge.
Chicago is averaging about 16 new COVID-19 cases per 100,000 residents per day.
At the same time, the statewide daily hospital admission rate has risen from about 30 COVID-19 patients per day to 34. It previously peaked at 861 in early January.
University of Chicago epidemiologist Dr. Emily Landon said the shift to focusing on hospital admission and case rates makes sense because testing numbers have been inflated by hospital-required tests for patients undergoing procedures, as opposed to people with potential COVID symptoms looking for a diagnosis.
“The testing figure has been diluted. It was a really good indicator in the beginning, but you have to adjust your metrics based on how people are behaving,” Landon said. She emphasized that residents shouldn’t abandon precautions just because the CDC has labeled their area a “low transmission” zone.
“Their job is to protect the greater good, not the individual good. If you have an immuno-compromising condition, or you live with someone who does, mask up, avoid crowds,” she said.
Dr. Michael Angarone, associate professor of medicine in the Division of Infectious Diseases at Northwestern Medicine, said the shift reflects a step toward “the living-with-the-virus kind of phase.”
“In some sense, it is endemic. It’s here, and we’ll have these periodic surges, but that doesn’t mean it’s less severe. It’s critical to get as many people vaccinated as possible,” Angarone said.
About 73% of Illinois residents are considered fully vaccinated.
For help finding a shot, visit chi.gov/covidvax or call the city’s COVID-19 hotline at 312-746-4835.
