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Are Michigan’s daily coronavirus (COVID-19) numbers accurate? Health officials respond

MDHHS responds to questions about COVID-19 case count accuracy

DETROIT – Many people have questioned the accuracy of state counts for daily coronavirus (COVID-19) cases, so Local 4 spoke to the Michigan Department of Health and Human Services to get a response.

Coronavirus cases are reported every day. Initial test results are sent to the Michigan Disease Surveillance System by the lab that performed the test. Once the data is tabulated by the computer, any remaining discrepancies are reviewed and resolved by staff members.

The process includes specific protocols to handle people who have more than one test or living in a different county than the one where they were tested.

The Michigan Disease Surveillance System is a person-centric system. So if someone is in the system with a COVID-19 infection from a previous laboratory, the system doesn’t create a new case if that same person has a positive test from another laboratory. It marries the additional laboratory information to the existing case, officials said.

That way, multiple tests for the same person only get counted as one case, according to Jim Collins, the director of the Communicable Disease Division.

“Staff from my division, every morning, our first thing is looking at the laboratories before we report out to make sure that cases that the system thinks might be the same, but can’t say with 100% confidence, are evaluated by human eyes,” Collins said.

Steps are also taken to ensure the case is attributed to the right county, Collins said.

“Our testing is based on the residence of the person,” Collins said. “There is an occasion where we don’t get an address for the person, and so initially, that referral goes to the country where the testing took place so we don’t lose referrals. In the process of following up, the case is identified, is given an address and if it’s in another county, that case then moves to the other county.”

Local 4 asked Collins why case counts are typically lower on Mondays.

“The national reference laboratories -- they’re running thousands and thousands and thousands of tests in single laboratories every day -- change their resource levels on the weekend, holidays,” Collins said. “I think that also there is a variance in the number of people seeking care and the number of tests being administered.”

There is a difference between the daily reported cases compared to the state graph of cases that shows cases by date of onset. The reason is the state recompiles the information by date of symptom onset compared to when the test returned positive, because it gives a more accurate picture of when the actual infections occur.

If cases sharply spike and the situation worsens, state officials said they’ll continue to fine-tune the automated duplication algorithms. But beyond that, if cases spike, the state will simply need to hire more people to do the manual work to ensure accurate numbers.


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