At the Bissell Point water treatment plant in north St. Louis, the focal point of the pump building is a small white refrigerator — about the size of a dorm fridge. Every 10 minutes or so, a mechanical, whirring scoop dips down into the influent sewage, pulls out about a tablespoon of water and drops it into a clear container about the size and shape of a milk jug.
Bissell Point cleans and treats everything that comes down the pipes when people on the city’s north side flush their toilets. But in the past two years the plant — and its mechanical water sampler — have also become a vital public health tool for monitoring the coronavirus. More than 1 million people throughout the region are submitting samples to the sewer district every day.
“This is really one of the only ways you can see what’s happening in the community, said Bess McCoy, a spokeswoman for the Metropolitan St. Louis Sewer District. “Not everyone is getting tested, but everyone is using the toilet.”
As fewer people are getting tested for the coronavirus, sewer shed surveillance remains one of the most accurate ways to show the virus still exists in the community.
The state and its partners at the University of Missouri are monitoring 112 sites, though some have dropped off and others have joined since the beginning of the project.
When someone is infected with the virus, traces are left in their feces. The samples aren’t contagious, but they are useful. Regular testing can show if the virus is spreading in the community and identify new dangerous strains.
An online dashboard shows that in about 20% of sites, the amount of viral particles in sewer sheds are increasing. In most of the collection points, the amount of virus is staying the same week to week and is still much lower than during early 2022, when the omicron variant was spreading throughout the state.
At Bissell Point, the particles have been slowly increasing since the beginning of summer.
Once those jugs in the pump house fill up, they’re carted to the lab, where a lab worker decants the water into smaller tubes, packs them into boxes with ice packs and hands them off to a courier who drives the samples to labs in Jefferson City and Columbia for testing.
Partners in poop
The plant has been collecting samples to test for the coronavirus since the start of the pandemic in spring 2020, said Jay Hoskins, MSD assistant director of engineering-environmental compliance.
“This idea of using wastewater as a mechanism to test the load … was something that everybody was interested in doing, because we wanted to get a better feel for how much viral material was out in the community,” he said.
Thanks in part to the enthusiasm of Mizzou scientists, Missouri has one of the most robust sewer shed monitoring programs in the country, Hoskins said.
“I think something like 60 to 70% of the population is in the sewer shed sampling program,” he said.
Hoskins said that information is more important now that people are not getting tested at the virus at doctors' offices, clinics and lab collection sites.
“More people are taking at-home tests,” he said, “And those at-home tests are not being reported to the health department.”
Wastewater testing shows what variants are existent in Missouri sewer systems that standard lab and patient tests don’t show. It predicted the rise of both the delta and omicron variants of the virus. The sewer shed surveillance dashboard shows omicron mutations in the sewers in most parts of the state.
Solid evidence
The information is interesting, but it’s of no help if public health officials aren’t using it to make decisions to keep their community healthy, epidemiologists said.
Health departments are using the information to make decisions, said University of Missouri microbiology professor Marc Johnson, who helped spearhead the state’s testing campaign and leads the wastewater testing lab at Mizzou.
“I always call it a reality check on where things really are,” Johnson said. “If numbers are going up or down, they want to know, is that a fluke or is that what’s really happening?”
For example, a health department could use a sewer shed map to figure out where to focus a mobile vaccination campaign.
“I know that the local superintendent had me on speed dial,” he said. “Every time he had to make a decision on masks, he wanted to be sure that I could provide a graph that would allow him to justify it.”
Challenges and opportunities
However, the practice is not without its challenges, said Aparna Keshaviah, a population health researcher who studies wastewater and epidemiology at the Rockefeller Foundation and the research firm Mathematica.
Keshaviah’s team surveyed dozens of public officials and wastewater treatment specialists about the benefits and challenges of coronavirus surveillance in watersheds.
As in much of the nation, nearly half of Missouri’s public health agencies with surveillance in place that responded to the survey had acted on that data to make health decisions, she said.
The team found that at small facilities, there aren’t always people to decode or share data with other departments, and many still rely on other metrics — like traditional case counts — to make policy decisions.
“Many officials are still struggling with how to interpret wastewater data and how to integrate it with other sources,” Keshaviah said. “More problematically, we've also heard that states are not always sharing the data and findings back to local agencies. So there's this real need for better reporting.”
Money could become an issue: Wastewater testing relies largely on funding from the Centers for Disease Control and Prevention. It’s unclear if the agency will continue to fund it in the years to come, which is worrisome for smaller plants with shoestring staffs and budgets.
“Right now we need to use the momentum of the pandemic and ramp up capacity at state labs … at universities and commercial labs, for a variety of things that could threaten public health,” Keshaviah said.
She hopes state and federal officials see the promise of studying sewage — which can be used to study other infectious diseases, antibiotic resistance and even opioid addiction.
Missourians can keep doing their part. All they have to do is flush.
Follow Sarah on Twitter: @Petit_smudge
