COVID source shout-out: CDC wastewater dashboard upgrades

After the CDC released its National Wastewater Surveillance System (NWSS) dashboard in February, the agency faced some criticism from scientists, data reporters, and others who found this dashboard didn’t actually do a very good job of presenting wastewater data. The initial dashboard only included one metric, percent change in wastewater levels over the last 15 days; without more context, it was difficult to understand where a high percent change was actually cause for concern.

But the CDC has responded to its criticism! This past Friday, the agency updated its wastewater dashboard to include a lot more context. Among the changes:

• You can now toggle between three metrics: the old percent change value, along with current virus levels in a site’s wastewater and the share of wastewater samples at a given site that tested positive for the coronavirus in the last 15 days.
• Clicking on a specific site provides users with a mini-chart of wastewater levels at that collection spot over the last few weeks.
• The dashboard lets you toggle on and off sites with no recent data and sites that started sampling during the Omicron wave.
• Above and below the dashboard, the CDC has added more definitions and explanations to help users understand what they’re looking at.

On Friday evening, I posted on Twitter, asking wastewater and data viz experts to weigh in on the updated dashboard:

wastewater people and/or data viz people, what are your thoughts on the updated CDC NWSS dashboard? is it clearer to read and interpret now? cc @COVIDPoops19 pic.twitter.com/xOoCWEVFdE

— betsy ladyzhets 📊 (@betsyladyzhets) April 8, 2022

Responses were mostly positive, with researchers saying that they were glad to see the CDC respond to criticism and add more information to the dashboard. Still, there’s more the agency can do, such as adding the population sizes covered by each site and, maybe, moving away from percentage changes as such a central metric.

To quote Claire Duvallet, data scientist at Biobot: “I think collapsing all three metrics to have the same units, and to choose percentage as that unit, is very confusing. Percentage changes are already so 🤯 to think about, & percentage changes of categories of percentages is just too much for my brain.”

I *really* appreciate the rapid response to public feedback from CDC NWSS & am happy to see this update, and actually think that the metric of "how high are recent samples relative to all other measurements from this site?" is a useful way to interpret WW data. https://t.co/tOznP5e6Nr

— Claire Duvallet (@cduvallet) April 8, 2022