As COVID-19 cases and hospitalizations due to the omicron variant climb to new heights, wastewater surveillance indicates some areas of the U.S. may have crested the wave.
In Wisconsin, the data has yet to indicate a peak. But used alongside case counts, public health experts say testing sewage for the virus can be an important tool in monitoring pandemic trends.
"It’s another dimension, another perspective that we can use, and potentially is an early warning sign where cases are increasing," said Ryan Westergaard, chief medical officer for the state Department of Health Services Bureau of Communicable Diseases.
A DHS dashboard that compiles data from wastewater treatment plants around the state launched in August. Right now, water samples from more than 60 sewersheds are being analyzed regularly for the coronavirus by staff at the Wisconsin State Lab of Hygiene and the University of Wisconsin-Milwaukee's School of Freshwater Sciences.
The samples aren't showing a sustained decline in prevalence of the virus yet, but those who work with the data are hopeful a downward trend will become apparent soon.
Sandra McLellan, a microbiologist in UWM's School of Freshwater Sciences who works with the wastewater samples, has noted a slight decline in two or three recent batches from Milwaukee's Jones Island treatment plant.
Jones Island serves about 470,000 people in the Milwaukee area. McLellan said she'd feel confident the data reflects a decline when it lasts two weeks, or about five rounds of samples, since it often fluctuates.
"We're not really seeing that in a lot of plants around Wisconsin yet, but we do see some indications a few samples are lower. I'm hoping by next week, we'll see them continue to drop," McLellan said.
A database from Biobot Analytics, a company monitoring wastewater data in many states, shows small declines in the prevalence of the virus in wastewater both nationally and in the Midwest from the week of Jan. 5 to Jan. 12.
Alternate look at prevalence of virus
Wastewater can be a reliable early indicator of a rise in cases before traditional testing numbers begin to reflect it. And, on the other side of the peak, a decline in cases.
And since everyone uses the bathroom, it's a good way to get a universal picture of the virus in the community instead of looking only at the people that seek out testing, experts say.
Plus, during certain times of the year, like the holidays, more people seek testing.
"Maybe a few months ago those cases maybe weren't recognized because people didn't get tested," McLellan said. "Wastewater, it's not relying on testing. It's always same, consistent measure of what's in the population," she said.
Widespread wastewater surveillance for diseases hasn't occurred before except in a few cases around the world, McLellan and Westergaard said.
"The question of wastewater treatment has been an interesting and frankly surprising success," Westergaard said.
McLellan is excited about the future of wastewater surveillance of infectious diseases. Her lab is testing for coronavirus variants as well as influenza to get a sense of their prevalence in the state.
She's even interested in monitoring things like a community's resistance to antibiotics.
"One of the things this pandemic has done is really opened our eyes to — 'hey, there is a way to monitor population health,'" McLellan said.
This article originally appeared on Milwaukee Journal Sentinel: Wastewater is an indicator of Wisconsin COVID, omicron trends