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By Karen in COVID —

Wastewater Wednesday - 3/12/25

Sorry about missing last week. Everything going on lately...well...it's just a lot. But I'm back at it today, and I promise I also have about five other posts on various topics in various stages of drafting that will be coming up soon! But let's get to it and see how things are going, 5 years out from the start of the pandemic.

COVID

The 💩 doesn't lie - it's been 5 years but COVID is still with us, and it's still a pandemic. The good news for this week, though, is that we're officially entering our spring lull:

COVID-19 Wastewater Surveillance in Wisconsin graph. 0 sites currently have a significant increase. The graph shows a steady decline in the concentration of SARS-CoV-2 in the wastewater in the preliminary data for the beginning of March.
Statewide wastewater graph from https://www.dhs.wisconsin.gov/covid-19/wastewater.htm

March - June is has typically been the time of lowest transmission, and is the best time to get unavoidable risky appointments like the dentist taken care of. I'm glad to see that the decline is continuing - for a while it had been looking like we were going to get stuck on a high plateau, but luckily that does not seem to be the case.

What is unfortunate, though, is that if you zoom out to the whole pandemic, our lulls are not dropping as low as they used to.

COVID-19 Wastewater Surveillance in Wisconsin - the graph from above has been adjusted to show the full duration of the pandemic - from the time wastewater collection started in September 2020 through March 2025. There is a spike followed by a long lull in summer 2021, followed by another spike that barely starts to decline before rising vertically to by far the highest peak of the pandemic (Delta followed by original Omicron). Then there is a steep decline in spring 2022, followed by a late summer increase that leads to a high plateau of mini spikes, followed by a decline into the spring/summer of 2023. The winter 2023-24 wave has the second highest spike of the pandemic, and is eventually followed by the late summer 2024 wave, and the winter '24-'25 wave which we are currently on the back side of.
Statewide wastewater tracking from the beginning of data collection in September 2020 through the present. https://www.dhs.wisconsin.gov/covid-19/wastewater.htm

It's hard to see, but if you go to the DHS website and explore the graph, you'll see that the first, long lull in 2021 hovered around 15-19MGC/person/day, with the lowest point being just 9MGC/person/day. The next lull, the short one after the Omicron wave, is around 16-17MGC/person/day. The summer 2023 lull is also around 16-17MGC/person/day. But then the lull in spring of 2024 is around 21-24MGC/person/day, and the dip we had in November 2024 never got below 26MGC/person/day.

Currently, we are at 39.2MGC/person/day. I hope that it continues to drop, but what this shows is that COVID is always circulating. It has never gone away, and even when there's less of it around, what actually qualifies as "less" is increasing.

Influenza

Our massive flu wave is also continuing to decrease, though we are STILL above last year's peak. I'm running out of time, so I'm not going to do a deep dive on the flu today, but know that you can check the data any time on the Wisconsin State Laboratory of Hygiene's website!

Stay safe out there, friends! COVID and flu aren't the only diseases we have to worry about these days, but a mask will protect you against almost all of them!

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