What is it?

The positivity rate of an area is a measure of how many tests are positive in the area where testing is occurring in a given time period, typically a week. As this measure increases, it indicates that more of those getting tested in an area are positive for the coronavirus.

Is there any context for it?

From a leaked White House report in July we know that the executive branch is classifying states’ coronavirus numbers at least in part through “binning” weekly positivity rate. They have three bins, signifying less than and greater than 5% and a third bin, greater than 10%. The last two bins are coded yellow and red zones. This is in line with the World Health Organization’s opinion of when the coronavirus is cause for concern. They list 5% positivity rate as being “too high.”

Does it have short-comings?

This measure is sensitive to more than one test being administered to a person, number of tests  available, and other factors. It is very possible for someone to get tested multiple times in a week, likewise it is possible that there be only enough tests for those with symptoms or probable exposure to the virus. Since the testing process is largely self-prescribed, meaning there is little to compel someone to get a test beyond their own desire to get a test, there is certainly an element of response bias inherent in this measure.

What does it look like in Georgia?

Georgia has been across the board in positivity rates. When tests were difficult to get, as the national supply was short and the virus was very new, rates were very high, around 1 in 4 tests were positive. We also had very few tests so the population of tests was not a good indicator. During April and May the positivity rate had declined from the red zone, through the yellow zone, and into the green zone, below 5% testing positive. During June, the positivity rate climbed up into the red zone, where it stayed through most of August.

What Happens Next?

If the Georgia positivity rate stays in the mid level bin, above 5% and below 10%, residents can expect that the number of new cases, deaths, and hospitalizations will follow. Conversely, the opposite would like see an increase in those metrics. If the positivity rate declines toward 0%, indicating that the virus is petering out, we will likely see a return to “life before the virus.” We will not predict what is going to happen to the positivity rate of this virus. If the positivity rate stays at the same level or decreases to below 5%, it is reasonable to expect Governor Kemp to continue to roll back restrictions. If the positivity rate increases, there is a possibility that Governor Kemp reintroduces restrictions such as was seen in June and July.