Scientists Are Monitoring Sewage For The Coronavirus More than 100 cities are monitoring sewage for the presence of the coronavirus, and public health officials think wastewater could provide an early warning system to help detect future spikes. NPR science correspondent Lauren Sommer explains how it works, and why scientists who specialize in wastewater-based epidemiology think it could be used to monitor community health in other ways.

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What You Flush Is Helping Track The Coronavirus

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What You Flush Is Helping Track The Coronavirus

What You Flush Is Helping Track The Coronavirus

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You're listening to SHORT WAVE from NPR.



Emily Kwong here with NPR science correspondent Lauren Sommer. Hey, Lauren.


KWONG: So for today's show, there's really only one place to start.

SOMMER: Yeah. It's a freezer full of poop.

STEPHANIE LOEB: So this is the negative-80 where we keep the samples.

SOMMER: That's Stephanie Loeb, a postdoc at Stanford University. She gave me a tour on Skype of that freezer in her lab.

LOEB: It's - yeah - very, very cold.

SOMMER: There's rows of boxes inside, each filled with small vials of, as she calls them, human solids.

LOEB: Yep. It's all sorts of shades of that same color, sometimes darker and sometimes lighter.

KWONG: OK. Thanks for painting that picture.

SOMMER: (Laughter)

KWONG: So why does this freezer of waste exist, Lauren?

SOMMER: Well, one of the problems with tracking the coronavirus pandemic has been sampling, right?

KWONG: Right.

SOMMER: We need to be checking a lot of people for the virus and often. Testing has been slow to ramp up in the U.S., but if you think about it, all of us provide biological samples every day.

KWONG: I see where you're going with this. You're talking about what we flush.

SOMMER: Yeah. There's actually a lot of information in our waste. There's a whole field called wastewater-based epidemiology that's working to track human pathogens using the sewage system. With the coronavirus, it's getting a lot of attention that Loeb says she does not normally get.

LOEB: I would say normally when I tell people I work with poo, they're not super interested (laughter).

KWONG: Yeah. I wasn't interested, but now that I know there's a whole field called wastewater-based epidemiology, I'm fascinated by this.

SOMMER: Yeah. And so that freezer, it has samples from 25 wastewater treatment plants around California, which means it's a health record for thousands and thousands of people.

KWONG: Gotcha. So you could use that as a collective sample and then test the deposits from all those people to see what's going on with the virus?

SOMMER: That's the idea.


BRETT GIROIR: So thank you, Mr. Chairman...

SOMMER: In a Senate hearing last week, Admiral Brett Giroir from the White House Coronavirus Task Force said this could help universities watch out for the virus if they reopen.


GIROIR: For example, wastewater from an entire dorm or an entire segment of a campus could be tested to determine whether there is coronavirus. So there are other strategies being developed...

KWONG: So today on the show, how our lowly sewage system could provide a frontline warning for how the coronavirus pandemic is spreading and maybe in the future for all kinds of public health problems. You're listening to SHORT WAVE, the daily science podcast from NPR.


KWONG: OK. Lauren, we hear a lot about how, when people have the coronavirus, it leaves their bodies through coughs and sneezes, but I guess it's also coming out your other end.

SOMMER: Yeah. That's what scientists are finding.


SOMMER: You shed virus in your solids. I'm using the jargon here.

KWONG: (Laughter).

SOMMER: I talked to one of the leaders of the Stanford project, Krista Wigginton, about what they're finding, and she says many researchers are looking right now at how transmissible the coronavirus is that way.

KRISTA WIGGINTON: These are probably particles, virus particles, that are mostly intact but that are no longer infective. That's kind of what it looks like at this point, but there is research coming out on this all the time.

SOMMER: Wigginton is a professor of environmental engineering at the University of Michigan, but she's visiting Stanford this year. And as soon as it looked like there was a chance the coronavirus was coming to the U.S., she and her fellow researchers knew they wanted to gather sewage samples before that happened so they could track it.

KWONG: So interesting. OK, so - but Wigginton said that fecal matter may not be infectious. Do we know that for sure?

SOMMER: Yeah. I mean, it's a really important question, and researchers are studying that right now because that's, obviously, a way that a lot of different viruses get transmitted - right? - which is...

KWONG: Yeah.

SOMMER: ...People not washing their hands, essentially.

KWONG: OK. So we got to still keep washing our hands. And I guess when Wigginton figured out that the coronavirus was coming to the U.S. and had this idea, I'm wondering how she got the samples. Like, did she call up a bunch of wastewater treatment plants and say, hey, can you please send us weekly deliveries of poop?

SOMMER: I mean, basically.


SOMMER: And she said the wastewater treatment plants were totally down...

KWONG: (Laughter).

SOMMER: ...Because, you know, they're pretty technical places. They do a lot of testing and sampling already because, you know, I mean, disinfection is their thing.

KWONG: Right.

SOMMER: So this made sense to them.

WIGGINTON: I think people realize that it's something that's been overlooked in the past. It's this perfect mix. You know, all - the entire community is putting samples in at the same time. It could really capture the health of the community or what's circulating in the community.

SOMMER: So what the wastewater treatment plants are doing is they gather sewage samples over a 24-hour period, they send them to Stanford, and then they test it by looking for the coronavirus' genetic material.

KWONG: So how much information can you really get about where the virus is spreading based on these solid samples? Because it doesn't seem like this would actually replace testing at a doctor's office.

SOMMER: No, it doesn't. I mean, that's still incredibly important. Wigginton sees this as just another layer of information that public health officials can use. You know, and maybe if the coronavirus hasn't shown up somewhere, you might spot it in the sewer system first, you know, kind of like a little early alert. That's how public health officials have used this technique already for polio in other countries because, you know, they're still trying to eradicate polio globally.

In a big pandemic like right now, you could be testing sewage over days or weeks, you know, to see if the virus levels are rising or falling. And maybe you could see those trends earlier than you would otherwise, you know, kind of like a surveillance system.

WIGGINTON: What's nice about that is it's a real-time measurement of what's happening in the community and what's being excreted in a community, where some other tools we have, like, you know, the number of confirmed cases in clinics. Sometimes those are delayed by quite a bit of time because people don't go get checked until maybe their illness has progressed quite a bit.

KWONG: So is this information from the depths of sewers being used by public health officials now?

SOMMER: The Stanford team is working on that, and another group is already providing that to some communities.

NEWSHA GHAELI: We have a lot of nicknames (laughter).

SOMMER: Newsha Ghaeli is co-founder of Biobot.

GHAELI: I think some of our customers joke around that, you know, we're the sewer girls.

SOMMER: Originally, the company was using sewage to monitor the opioid crisis, trying to give communities tools to see how severe that is. But when the coronavirus broke out, they started offering to test for that. And now they're testing sewage for around 150 communities across the U.S.

GHAELI: Even once we do open up our cities again and we do go back to work again, it's very valuable for us to have a robust surveillance system in place to help contain any outbreaks that may happen in the future.

SOMMER: And, you know, there's a much deeper idea in the science behind all this work. It's something Ghaeli started thinking about when she was working on urban studies at MIT, where she met her co-founder, Mariana Matus.

GHAELI: When I met Mariana and she was working on this science - wastewater-based epidemiology - I had never heard of it before. But to me, it was a real moment of realizing that, wow, this is huge. This will transform our cities one day, and I want to be a part of working on it.

SOMMER: And for Matus, this whole idea is about representing people who may not have easy access to health care.

MARIANA MATUS: Every person that is using the toilet has a voice in this data set.


MATUS: And they can be taken into account for public health resources and prioritization of resources for people.

SOMMER: Matus told me, growing up in Mexico City, she saw and felt firsthand what it's like not to benefit equally from public health resources.

MATUS: And I think that it's just a space that I hope we can change and we can really make it to be data-driven, make it to be more fair and make it to be more effective. And I would say that's what makes me really, like, wake up full of energy every day, is to imagine that future.

KWONG: Ah. OK. So sewage is kind of an equalizer for them? At least, that people with access to sanitation and plumbing can have their health reflected in the data.

SOMMER: Yeah, which is why she and Ghaeli see this idea going far beyond the coronavirus. As they see it, each wastewater treatment plant could be a sentinel for their community, part of this bigger network monitoring all sorts of public health issues in this collective way. And Ghaeli says, you know, as a first step, they were able to detect coronavirus in communities the same week the first test came back positive.


SOMMER: What Biobot is trying to do now is use sewage to estimate the specific number of people who have the coronavirus in a community, as in, you know, we think 10,000 people are infected, for example.

KWONG: Oh. That sounds kind of hard to figure out, you know, because you'd have to determine how much virus a person is flushing to do the math of how many people that sample represents.

SOMMER: Yeah. You have to figure out the math, basically. And that science is still evolving because some people seem to deposit a lot of virus compared to others, and some people shed virus for weeks longer than others. And then there's this whole system of the sewage pipes to think about. I mean, the travel time from a house to a sewage treatment plant - it may take a while. So does the virus break down?

KWONG: Mmm hmm.

SOMMER: You've also got some cities where, when it rains, the stormwater goes into the sewage system. So that could actually dilute your samples.

KWONG: That's a lot of variables.

SOMMER: Yeah. So Biobot is still experimenting with this. And they're trying to figure out how to make this kind of sampling a solid way to track the number of people who have the virus.

KWONG: Solid?

SOMMER: Emily, we almost made it through this whole thing...

KWONG: (Laughter).

SOMMER: ...Without doing - I'm not going to go there.

KWONG: I had to sneak in one. I had to. I've been so good.


KWONG: OK. So, Lauren, you mentioned that Biobot is working with 150 communities, about. You have that project at Stanford. So do you think this metric - what the sewage says - will be used by communities in the months ahead when it comes to fighting this pandemic?

SOMMER: Well, I called one community that's trying to use this information from Biobot - the Miami-Dade Water and Sewer Department in Florida. Doug Yoder is deputy director there, and he's been sending samples to Biobot for over a month now. He says the virus numbers they've been getting back have been going up and down - you know, way up one week, down the next. So, so far, it's been hard to pick out that clear curve - you know, that goes up, up, up, up - like you see with some of the clinical testing data that we have out there.

DOUG YODER: This data may not yet be ready for primetime in terms of community decision-making but definitely has potential and promise for being able to see trends.

KWONG: So we're not going to be seeing sewage numbers anytime soon as part of our daily update of coronavirus data.

SOMMER: Yeah, maybe not. I mean, he says health officials are very interested in getting that kind of information because, you know, testing is still not reaching everyone in the community equally yet in, you know, this really widespread way that needs to happen. I mean, communities are trying to gauge whether they're seeing new surges as they start opening up, right? Because they want to know if they need to put in a new lockdown. The key will be spotting those surges early. So having reliable, early information, you know, even if it's from sewage, could potentially be key in the future.


SOMMER: Well, Lauren Sommer, thank you for this reporting, and, of course, for keeping it clean.

SOMMER: It was tough, but you're welcome.

KWONG: (Laughter).

This episode was produced by Brit Hanson and Brent Baughman, with fact-checking by Emily Vaughn and editing by Viet Le. I'm Emily Kwong. Thanks for listening to SHORT WAVE from NPR.

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