New accounting fuels hope that coronavirus is better contained in Michigan

Michigan public health officials have altered how they report positive coronavirus tests in the state, changes that show fewer people have been infected in recent weeks than previously reported.

The change, announced this weekend, doesn’t not lower the number of confirmed coronavirus cases, which rose by 202 on Sunday to 54,881. But it shows the percentage of people who have tested positive for an active infection has fallen further than earlier reported.

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Before the change, the state reported that 7.7 percent tests were positive in the last week. With the change, that percentage falls to 6.7 percent, with the most recent day reported, Friday, at 4.2 percent.

A lower rate of positive tests is good news because it suggests testing is more widespread and the virus is better contained.

Michigan, like many states, had until now combined the number of people who tested positive for an active infection with those for whose tests indicated they had previously contracted COVID-19.

The latter test, called a serology or antibody test, detects antibodies tied to previous exposure to the virus and suggests the person has recovered and is not likely to spread the virus. 

Here’s why it’s important: One of the metrics Gov. Gretchen Whitmer has used to gradually reopen the economy is whether the percent of people who test positive for COVID-19 steadily falls and remains below 10 percent. Michigan had seen positive tests fall for weeks but, on May 13, the state reported that it had spiked to 13.2 percent.

It turns out that jump was based on the inclusion of nearly 6,500 serology tests, of which 35 percent were positive. The actual positive test rate for people with an active infection that day was 5.3 percent, the new numbers show.

By combining the results from two tests, it can make it look like more tests are being conducted and widespread testing has been a goal to reopen more of the economy. But to control the spread of the virus, public health officials need to be able to accurately track who currently has the virus, separate from those who have recovered. 

Combining results from those two tests led epidemiologists to recently criticize the Centers for Disease Control and Prevention, which gathers COVID-19 data from the states and was likewise combining the tests in its reporting. In addition to Michigan, health officials in Virginia, Texas, Georgia and Vermont also said they would separate the two tests.

Michigan made the change in its daily data release Saturday and sent a press release later Saturday during the holiday weekend explaining the change.

“Accuracy and transparency are paramount as we continue to respond to this pandemic,” said Dr. Joneigh Khaldun, chief medical executive and chief deputy for health. “We continue to expand and improve data reporting to make sure the public understands where their community stands with the COVID-19 outbreak.”

On Sunday, the state reported the fewest number of deaths since March, with just 5. The numbers have steadily fallen since the peak of the pandemic in late March and early April but weekend reporting numbers have typically been lower than weekday reports.