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CHAMPAIGN — If you’re confused about the discrepancies in daily COVID-19 case reporting by the University of Illinois and the Champaign-Urbana Public Health District, you’re not alone.

But there’s an important reason the daily totals don’t match, according to a public health official.

Take Sept. 4, for example: That was a day the University of Illinois reported 104 new positive saliva tests on campus — on the same day the Champaign-Urbana Public Health District reported 88 new positive cases for all of Champaign County.

Awais Vaid, deputy administrator at the public health district, said the UI reports positive tests immediately, while the public health district takes a few days investigating the details of each positive test before adding a single positive case.

“We only report cases once we have completed our investigation, and we will not match for a few days,” he said.

The data provided by the UI is reflected in unique positive cases — but only unique positives for the saliva test being done on campus. The UI doesn’t have access to testing results for its students and staff who may have tested positive elsewhere — for example, at the state’s free testing site at Market Place Mall.

“Unique new cases are the first time an individual is detected COVID-19 positive by the SHIELD saliva test,” the UI data dashboard states.

For public health investigators, a new unique case is someone who has tested positive for the first time, regardless of the testing method and testing location.

Say a student tested positive at the drive-thru test site in Champaign or in their home communities over the summer, then tested positive in saliva testing after arriving on campus.

Champaign County wouldn’t count that new positive on campus, because it’s already been counted, Vaid said.

What’s most misunderstood about the data is this, according to Vaid: “I think the biggest thing is the difference between a positive test and a positive case,” he said. “A positive test doesn’t necessarily mean a positive case.”

It’s also possible for those who tested positive in recent months to test positive again — even after they are no longer contagious, he said.

People are most actively contagious 48 hours before and 48 hours after they show symptoms, and are usually not considered to be infectious after about 10 days, Vaid said.

But the virus can remain in the body in a dead form for much longer, even for months, showing up as a positive test in someone who would be past the point of being able to spread the disease, he said.

Also part of public health’s investigation into each positive test is whether that person has COVID-19 symptoms and where that person lives, regardless of where they were tested.

That’s important, because verified new positive cases add to the totals in counties where people live, not where they work or test positive or end up in the hospital.

UI students are counted as residents of Champaign County while they’re living in Champaign County, so many of those unique new COVID-19 cases turning up in UI testing data will make their way into the Champaign County totals after public health has verified they are unique new cases and not repeat positive tests.

But a number of people employed on campus and elsewhere in Champaign County live in other counties, Vaid said.

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