Public health providers hope testing wastewater will alert them to next COVID-19 spike
‘We’re figuring out the science as we go,’ says DHS official
Wastewater treatment plant (Michal Jarmoluk | Pixabay)
As COVID-19 cases continue to ease in Wisconsin and public health officials cast a wary eye toward the possibility of a new increase, tracking the virus in wastewater is taking on new importance.
“It can kind of give us a kind of an early peek … at what we may be seeing later on, with cases that are diagnosed and reported to public health,” said Dr. Jonathan Meiman or the Wisconsin Department of Health Services (DHS) in a briefing with reporters Friday.
Wastewater surveillance involves sampling wastewater and sending it to a lab to be analyzed for the concentration of SARS-CoV-2 virus. The technique can serve as a leading indicator of increasing COVID-19 cases, according to Meiman, who is chief medical officer for DHS and the state epidemiologist for environmental and occupational health.
That’s especially useful when cases are low and fewer people are seeking tests for the illness, he said.
“As we get farther into this pandemic, and COVID-19 becomes endemic, as people may be less likely to seek testing or they may be doing more home testing, we don’t get the results to public health [agencies],” Meiman said — so that official data on cases might undercount the prevalence of the disease.
The method offers an alternative — not a substitute for other ways of measuring the pandemic, but a supplement, Meiman said. “It’s an independent way of looking at transmission within communities.”
COVID-19 case information shows the disease is continuing to decline in Wisconsin. The new assessment standards at the Centers for Disease Control and Prevention (CDC) have measured COVID-19 community levels as “low” in 70 of Wisconsin’s 72 counties as of the agency’s weekly update on Thursday, March 17,
DHS measures COVID-19 activity in the state differently, but the state health department’s approach also shows the trajectory falling in Wisconsin, and in a growing number of counties the virus spread has decreased to “medium” from “high,” according to a weekly update posted Wednesday, March 16.
On average over the seven days that ended Thursday, there were 338 new cases recorded per day, down from a seven-day-average of 394 a week earlier, March 10, DHS reported.
At the same time, however, cases have been rising again in Europe, attributed to an offshoot of the virus’ most recent major variant, labeled omicron. The Washington Post reported Wednesday that U.S. public health officials are watching for the variant, known as BA.2, and in Florida it has already surfaced.
Meiman said that if wastewater surveillance shows evidence of an increase in cases, public health agencies can alert communities that the virus is spreading. For the general public, getting those messages will be important “because there are a lot of things that people can do to protect themselves,” he said — from getting vaccinated or a booster to seeking a test or treatment in the event of symptoms.
“Now we have very effective medications for the treatment of COVID-19,” Meiman said. If testing shows an increase in community transmission, “if you’re somebody who is at high risk, it’s very important to get tested so you can get access to that treatment, which really helps prevent severe disease.”
Wisconsin was among early states to adopt COVID-19 wastewater surveillance. The state’s project is a joint effort of DHS, the Wisconsin State Laboratory of Hygiene and the University of Wisconsin-Milwaukee School of Freshwater Sciences. It’s part of a national program, and participants hope that over time, it will lead to “a more robust and national surveillance system,” said Meiman.
“We’re figuring out the science as we go,” he added, as DHS works to understand how to best interpret shifts in the readings from day to day or week to week.
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Readings from the tests posted on the state’s website showed increases in concentrations in several communities across the state in the second week of March. For several of those, “it’s probably too early to tell” whether the higher readings are cause for concern, Meiman observed.
Virus levels in wastewater have been low in Wisconsin in recent weeks, and what looks like a large increase might only be a proportionally a big jump relative to those lower readings, he explained
In some other locations, including Green Bay and Milwaukee’s Jones Island treatment plant, “those are sites where we’re seeing some consistent increase … that would be indicative of increasing community transmission of COVID-19.”
The data fluctuate, however. A few hours after Meiman’s briefing, an update on the DHS wastewater testing map showed that in several communities where increases had been reported previously, the latest readings showed that concentrations of the virus were leveling off.
At treatment plants serving a larger population, the program tests samples twice a week. Smaller-volume plants might be tested once a week, but DHS and its partners in the project are shooting for twice-a-week tests in more places because it can produce better trend information, Meiman said.
Lab analysts have been able to use genetic markers to look for variants of the virus, including those that have been particularly contagious. More complex analysis that includes sequencing the genetic code is “an emerging area,” Meiman said, which the state hygiene lab is working on. Being able to identify variants in the wastewater is “ultimately where we want to go.”
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