Backlog in COVID-19 test reporting leads to Illinois’ highest daily caseload ever — 5,368 — and reveals stretch rivaling numbers in May

Public health officials on Friday blamed a slowdown in Illinois’ coronavirus test reporting system for the state’s largest-ever batch of new COVID-19 cases reported in a single day: 5,368.

The unprecedented caseload was confirmed among a whopping 149,273 tests reported by the Illinois Department of Public Health, the result of a backlog that officials say they discovered earlier this week.

Labs submit their test results electronically to the state every day, but the state’s data processing system began working “slower than normal” on Tuesday, according to Derek Lindblom, head of the state’s testing team.

By the time the delay was cleared Thursday afternoon, a testing backlog of up to two days had piled up, Lindblom said.

“Even a short delay of a day or a day and a half in processing will lead to a significant increase in test reporting,” Lindblom said.

Friday’s daily case count soared past the previous high of 4,014 new cases reported at Illinois’ initial height of the pandemic May 12. And the test count dwarfed the state’s previous high of 56,766 tests reported Aug. 22.

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Still, the unloaded backlog actually lowered the state’s average testing positivity rate over the last week to 4.1%, down three notches from Illinois’ rolling rate as of Thursday.

Lindblom said the backlog wouldn’t affect the positivity rates for individual counties or regions. Those are the numbers experts use to gauge how quickly the virus is spreading.

“The tests are still the exact same tests. There was just a delay in the processing of the tests,” Lindblom said. “The trailing averages are all the same, which is what our decision-makers use.”

But the testing pileup does explain in part why the state reported only 1,360 cases Thursday, Illinois’ lowest daily number in more than three weeks.

And while inflated, the new cases reported on Friday still put the state in a dangerous position. If the backlog only began on Tuesday, as officials say, that means the state averaged 2,587 new cases over the past four days. That’s not far off from a peak four-day stretch in May when Illinois was reporting 2,841 cases per day.

Jordan Abudayyeh, press secretary for Gov. J.B. Pritzker, countered that the statewide positivity rate “has remained fairly stable this week” and said the apparent uptick in cases “is generally proportionate to the growth in tests.”

“But the Governor is watching the data closely leading up to the holiday weekend,” Abudayyeh said in an email.

Anthony Vazquez/Sun-Times file

Tech upgrades made to the processing system give the state “plenty of running room in the future” as Illinois remains among the top few states nationwide in overall testing capacity, especially with a new rapid saliva test in use at the University of Illinois, Lindblom said.

The state health department on Friday also announced the virus has killed 29 more people in Illinois, while the same number of Illinois counties are at a coronavirus “warning level” — about a third of the state map.

Suburban Cook County worked its way off the warning list that it had landed on a week earlier, but north suburban Lake County was added as the result of two “risk indicators:” a rate of 95 cases per 100,000 residents — over the target rate of 50 cases — and a sizable increase in COVID-19 deaths over the previous week.

Lake County Health Department executive director Mark Pfister called it “a wake-up call heading into Labor Day weekend.

“We need everyone to wear a mask, wash their hands often and watch their distance. Reconsider your plans if they include risky activities and gatherings,” Pfister said in a statement.

Far southwest suburban Will County remained on the list a week after Pritzker banned indoor dining in the region due to soaring positivity rates. Along with Kankakee County, its regional positivity is at 8.7%

The other “warning level” counties span Illinois but are largely clustered downstate: Boone, Bureau, Clinton, Coles, Cumberland, Edgar, Effingham, Fayette, Greene, Henry, Jasper, Jefferson, Jersey, Lake, Lawrence, Madison, McLean, Monroe, Pulaski, Randolph, Rock Island, Shelby, Stark, St. Clair, Union, Wabash, Warren and Williamson.

Ashlee Rezin Garcia/Sun-Times file

Outbreaks there have been tied to college parties, weddings and bars, while “general transmission of the virus in the community is also increasing,” according to the state health department.

Chicago’s testing positivity rate has held steady at 5.6%, while suburban Cook is at 6.9%.

Over the last five months, 4.3 million people have been tested for COVID-19 in Illinois, at least 245,371 have tested positive and 8,143 of those have died.

The state’s latest figures on “probable” but untested cases suggest the virus has killed an additional 219 people and infected another 1,928. The overall recovery rate is 96%.

As of Thursday night, 1,621 Illinois coronavirus patients were hospitalized, with 360 in intensive care units and 155 on ventilators — all well within capacity.