Public health experts call out confusing COVID-19 data maps; DPH set to make changes

ATLANTA — The Georgia Department of Health says it’s making a number of data visualization changes in the coming week in an effort to make the state’s COVID-19 stats easier for the public to understand. The state website changes come amid criticism from public health experts regarding color-coded mapping.

“I think there’s a responsible way to do this. There’s an irresponsible way to do this. And the way they’re doing it is both irresponsible and misleading,” said Dr. Harry J. Heiman, a professor and program director with Georgia State University’s School of Public Health.

A July 17 tweet pointed out two color-coded maps that, when put side by side, appeared the same but actually represented a vast increase in COVID-19 cases across Georgia.

That’s because the color mapping looks identical, but the legend showing COVID-19 numbers represented different ranges representing the same colors.

In this instance, the same map in appearance actually represented a 49% increase in COVID-19 cases. Unless displayed side by side by the user, a glance at the map would not indicate the increase.


“To be honest, public health experts have been pointing out to the Department of Public Health, literally for months, that there are problems with data visualization,” said Heiman. “And, you know, if you understand what best practices are around, consistent presentation of results in a way that both professional and lay users can understand them, what we’re seeing, particularly in regard to the maps, and the changing in the values associated with different colors is not a reflection of best practices. In fact, I would say it’s a reflection of, of worst practices.”

The color mapping practices have come under fire within the department itself, but for different reasons.

Dr. Amber Schmidtke is a former Mercer University professor who works as a volunteer adviser for the state’s COVID-19 data task force.

She also presents the same DPH data on an independent website to make it easier for the average Joe to read.

Schmidtke pointed us to a recent post, where she tells followers she works with DPH data charts but is not a decision-maker in what ultimately posts to the state website.

Schmidtke says the DPH maps “don’t have as much value because they’re not showing cumulative data.” Using Albany as an example, she points out it “will appear to be a hot spot for months because of April spikes,” only making it useful for historical perspective.

“If we really want to get upset about something with the state and Department of Public Health we should be demanding more timely maps that better account for what is happening on the ground,” Schmidtke wrote. “I’ve been arguing for this for a while, along with several of my colleagues within the DPH.”

In a statement, DPH spokeswoman Nancy Nydam echoed Schmidtke’s point about the maps in question, and their purpose.

“These maps are not designed to show increases over time, but rather to show density by location and differences between counties,” Nydam wrote.

“They should not be compared to each other,” she continued. “If the ranges are not periodically reset, the entire map would end up one color and viewers wouldn’t be able to make distinctions between locations.”

Long-term trends are visible on a curve in a different location on the DPH website.

Still DPH tells Channel 2 investigative reporter Nicole Carr that they are making changes amid criticism and concern over providing more clear and transparent data.

They’re in the process of developing a new map that presents two-week incidence. In other words, they’ll divide the rate of cases by population to give a better picture of current disease spread trends. The department is also adjusting scales monthly instead of daily to help make better comparisons over time. This will include presenting previous maps next to new maps when scales are reset. Finally, when it comes the actual color codes, Nydam said categorization schemes will change to make better comparisons between Georgia counties.

Nydam told Carr the department is hoping the changes will be displayed on the website next week.