Illinois' coronavirus data looks a little different as health officials have changed the way they report new cases and deaths, adding "probable" infections and fatalities to the count.
But what exactly makes a coronavirus case a "probable" one and why is Illinois reporting them now?
Beginning last Friday, officials began including "confirmed cases and probable cases combined" under guidance from the Centers for Disease Control and Prevention.
"A confirmed case is laboratory confirmed via molecular test. A probable case meets clinical criteria AND is epidemiologically linked, or has a positive antigen test," IDPH said in announcing the new cases and change in reporting. "If a probable case is later confirmed, the case will be deduplicated and will only be counted once. Probable deaths and confirmed deaths will continue to be reported separately."
A large portion of the state's "probable" cases came from an increase in antigen testing across the state, in part sparking the change in reporting, according to IDPH Director Dr. Ngozi Ezike.
"With the the advent of a large amount of this resource of the rapid antigen tests, per the CDC definitions, when you get that positive test, that is listed as a probable case," she noted during a briefing Tuesday. "The confirmed cases are molecular tests."
Illinois began distributing rapid antigen tests from the federal government last month, and the state's top doctor expects as more of those tests are conducted "we will get more probable cases."
"Now that we have gotten hundreds of thousands of tests from the federal government, and we've been passing those out to local health departments in different places where we're piloting its use, those are not considered when you get the positive test in that those are not considered confirmed cases, those are called probable cases," Ezike said. "But we are treating - I mean, that is a positive. You have COVID if you come up with a positive test on that BinaxNOW test. So that is part of our caseload in terms of people who now have been diagnosed with COVID, and that we need to identify their contacts and that they need to isolate, etc. So total will now be the combination of confirmed cases, plus probable cases."
"The antigen test, particularly the ones that the federal government has distributed to us and to many other states, are a little less sensitive than the PCR tests," Illinois Gov. J.B. Pritzker said Friday. "So that's why they're, you know, slightly, I don't want to say they're less accurate - I mean, they have a different sensitivity level. And the result is that that's why they've been labeled slightly differently. But if you get an antigen test done, and it tests you positive, it is very, very likely that you are a positive."
In addition, the state has added all probable cases from the pandemic so far to its total number of cases, meaning the statewide total increased by 7,600.
"If we go back, trying to remember the time where we didn't have 100,000 tests a day, there was a time when we said, if you have the symptoms, you're around somebody who has COVID, you have the fever, you have this, you have that - you have COVID. You don't need to get a test, partly because we didn't have access for everyone," Ezike said. "So those individuals that were made known to the local health department also got listed as probable cases because they were linked to someone who was known to have it, but didn't have a confirmatory test. So those probable cases had been counted, but we've never included them. Now, we're bringing all of that data back for probable cases - the antigen forms, probable cases - and putting it with our confirmed cases from the molecular test."
With the change, Illinois has since reported more than 10,000 new coronavirus cases, topping 12,000 on Tuesday - a state record.
On Friday, however, the state added nearly 18,000 cases to its total, despite only reporting just over 10,000 new cases. According to the health department, the statewide total was adjusted to reflect previous "probable" cases from earlier in the pandemic.
As of Tuesday 511,183 cases had been reported since the pandemic began and the death toll stood at 10,289, IDPH said.