What's the COVID-19 'positivity rate' and who determines it?

Posted at 5:04 PM, Nov 25, 2020

There is no federal standard for calculating a state's COVID-19 positivity rate, which means states have come up with their own indicators to calculate the percentage of COVID-19 positive cases, per population ratio.

Different data used has shown some discrepancies, like Kentucky reporting Ohio's positivity rate at 15% when it added the state to their COVID-19 travel advisory list on Tuesday. At the same time Kentucky issued this rate, the Ohio Department of Health reported the state's rate was 14%.

Each state uses different ingredients to calculate this rate, making it difficult to fairly compare on a state by state basis; John Hopkins University researchers have found four ways to calculate a positivity rate.

"On average positivity rates are about 12% in the county as a whole," said Greg Kesterman, commissioner of Hamilton County Public Health. "Closer to 15% when you look at the suburbs and closer to 10% when you look at the City of Cincinnati proper."

To make matters even more complicated, Hamilton County's health commissioner said the county relies on another set of data that shows rates above and below state numbers.

"I pretty much solely refer to the data that is pulled together by the health collaborative and I feel very strongly that that data is accurate and calculated correctly," said Kesterman.

The Tri-State region has also indicated a difference in rate reporting with data on Indiana. However, although the discrepancies exist, they are not different from one another enough to truly impact what that data means, which is that cases, deaths and hospitalizations are on the rise in all three states.

"The message doesn't change at all," said Kesterman. "No matter where you go if you're traveling, we're asking you to be careful."

Throughout all three states, one recommendation remains the same: Travel for pleasure should be postponed.