‘You need to be patient’: COVID-19 wastewater scientist says it’s too soon to tell if Madison is past Omicron peak

MADISON, Wis. — Throughout the course of the pandemic, scientists have relied on a number of ways to track the spread of COVID-19 including PCR nasal tests, rapid tests, and contact tracing, among others.

One method, though, has given researchers a look at COVID-19 on a community-wide level without swabbing a single nose: wastewater monitoring.

“Wastewater is a great snapshot of the community, and it can tell us a lot about people who are asymptomatic or not testing,” Dagmara Antkiewicz, a scientist who’s worked with the Wisconsin State Lab of Hygiene’s COVID-19 Wastewater Surveillance Program since its launch, said. “So it’s a good, well-mixed sample from the whole entire community because everybody goes to the bathroom.”

One thing wastewater monitoring can’t do, at least based on the latest data, is determine if Wisconsin has made it past Omicron’s peak.

Data from the Wisconsin Department of Health Services’ Coronavirus Wastewater Monitoring Network page seems to show a considerable decline in the virus’ presence in Madison’s sewage system, but Antkiewicz cautioned against relying on the visual graph because the data behind it is sourced in complicated ways.

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Because wastewater samples include a mix of everything that gets flushed down a drain, it can be difficult to isolate the genetic material that scientists are looking for to study the virus’ presence. Things like industrial waste, hospital disinfectants, cleaning agents and degreasing agents — all of which often end in the same place — easily get mixed in with the human waste, either muddying or eliminating any genetic material needed to detect the virus.

It’s because of those variables that Antkiewicz said interpreting any visual dips in the virus’ prevalence, as of now, is jumping the gun. It’s simply too soon to tell if that decline is because of declining infections on a local level or if there are other elements within a sample that are causing the virus’ presence to read lower than it actually is.

“As a state, I would say we’re not past the peak yet, just that’s how it’s looking. Whether Madison is maybe turning the corner faster, I would want to hope with everybody else, but we don’t know that yet,” Antkiewicz said. “We’ll need another week, or two maybe, of data to really see where it’s going.”

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To address the varying data collected from wastewater facilities, the CDC and DHS created a significance analysis tool to help determine if rising or falling concentrations of the virus were significant or not.

As of the dashboard’s latest update (Jan. 14), wastewater from Madison’s treatment centers showed “no significant change” in the concentration of Sars-CoV-2.

Of the 10 wastewater systems that showed a significant change in Sars-CoV-2 concentration during a similar time span, nine of them saw either an increase or sustained increase in virus concentration, according to data from the dashboard. Only one system, De Pere’s Wastewater Treatment Facility, saw a sustained decrease during the same period.

“You need to be patient with judging the trends, and that’s what the significance analysis is for,” Antkiewicz said.

Late last week, health officials in Rock County said wastewater monitoring led them to believe COVID-19 is much more prevalent in the community now than it ever has been.