Q&A: Ohio health officials already test wastewater for COVID. Now they look for the flu
There's a lot to learn from poop.
That's why Ohio has been monitoring wastewater for COVID-19 since 2020, and why this year the state expanded the effort to monitor for flu.
In Cincinnati, the city health department already found flu type A, the more severe form of the virus, in wastewater collected from Cincinnati’s Mill Creek wastewater treatment plant.
Kim Wright, supervising epidemiologist at the Cincinnati Health Department, spoke to The Enquirer about the differences between detecting COVID-19 and flu in wastewater and what we can tell from the data now. Questions and answers were edited for clarity and length.
Q: When the Ohio Department of Health tests wastewater samples, is it a simple finding the virus being present or not, or does the concentration of the virus also matter?
The department is getting two samples per week, and these are the same samples that are being collected for the COVID wastewater analysis.
With the COVID data, they’re looking at the levels over time, but they’re also looking to illustrate if the level is increasing, substantially increasing, holding steady, or declining. So that’s the way we’re used to seeing it presented from the COVID dashboard.
With the influenza, the Ohio Department of Health is learning how to analyze that. Apparently it’s a little harder to detect in wastewater, so the way that the department is alerting the public about is if they’re seeing a sustained higher level of influenza over a few weeks time.
Is the data for flu wastewater detection difficult to understand?
I think there’s a learning curve. It took us a little bit to learn how to interpret the COVID data from the wastewater. We’ve been looking at that since June of 2020.
Trends over time are what we like to look at from an epidemiological standpoint. Are we trending up, or are we trending down? How does this look compared to last year? This is a brand new thing. It’s going to take a little while to collect some weeks’ worth of data before we really feel comfortable with how we’re interpreting it.
How does flu in the wastewater compare to other indicators that you have? Flu isn’t like COVID in that people don’t really test for it.
With COVID, we rely heavily on test results. But overall, I would say fewer people are interested in if they are positive for COVID or not, compared to a few years ago, when all the testing was reported and captured, and that was a good indicator of the community transmission of COVID.
Now, wastewater is a better indicator of community transmission. In some cases, you can see the wastewater actually has a little bit of a predictive value. We would see the COVID in wastewater rise up just ahead of the clinical test numbers going up.
With flu, there’s a lot of indicators. If you go to the Department of Health for Ohio or CDC, they’re looking at the percentage of outpatient visits that were attributed to influenza-like activity, thermometer sales, percentage of emergency department visits, hospitalizations. We have a lot of other indicators for flu, and I wouldn’t be able to say if the wastewater will be more or less accurate this early in the game.
But over time, what we can do is look back and say, "What did wastewater do during these periods with these other indicators? Was wastewater as accurate, or did it have some predictive value?" The verdict’s still out on that.
This article originally appeared on Cincinnati Enquirer: Poop is a good way to measure COVID. The jury's still out on flu
