August 31, 2022

Wastewater epidemiology: something in the wastewater

By Conor McKechnie and Dodi Axelson

Wastewater epidemiology: something in the wastewater

Wastewater-based epidemiology is a relatively new approach to determine the viral make up in any given area. Using chemical analysis of pollutants and biomarkers in raw wastewater, the level of exposure to certain pathogens can be assessed. This technique was used during the pandemic, which has helped realize its potential in public healthcare policy.

We speak to Prof. Dominic Frigon, a specialist of biological wastewater resource recovery at McGill University, who used this technique in Quebec through the pandemic to determine areas of vulnerability, including a homeless shelter. We also speak to Dr Kata Farkas, an environmental virologist at Bangor University, to understand the wider applications and importance of this analysis technique.

Urine for a treat with this conversation.

CONOR: Dodi, we start today's episode in Barcelona.

DODI: Very nice. Very nice.

CONOR: Yeah, the year is 2017. And the European Monitoring Centre for Drugs and Drug Addiction, EMCDDA...

DODI: ...As we usually say.

CONOR: Have just finished their annual report and they have found that the Catalan city was Europe's capital of cocaine consumption.

DODI: Okay, that's not a normal topic for Discovery Matters. Is this what matters today?

CONOR: Sort of, yes. But not really. It's kind of exactly how the city's predilection for illicit drugs was really discovered.

DODI: Okay, how was it?

CONOR: Sewage. They looked at the city's wastewater, they measured drug residue and this form of wastewater monitoring – analysis that monitors in real time the way the city and its inhabitants live through the water they consume and the water they flush – is also known as wastewater-based epidemiology.

DODI: Again, with the poop!

CONOR: Yeah, and not just poop, its wee as well and everything we flushed down the toilet. So, wastewater monitoring is what matters on today's episode of Discovery Matters. So, bye bye Barcelona for now. Let's head over to Canada for a more recent case of studying wastewater.

DOMINIC FRIGON: We've been analyzing the wastewater in the province of Quebec for the presence of SARS-CoV-2, which is the agent of COVID-19.

CONOR: This is Dominic Frigon, a professor at the McGill University and a specialist of biological wastewater resource recovery.

DOMINIC FRIGON: With the change in concentration, we actually can tell the change in circulation of the virus in the population. And you know, do we have an increase in case numbers. So, we cannot say per se the number of cases that we have, but we can actually find the trends of the pandemic in a given population.

CONOR: In fact, he and his team instigated the level of alert to decide on lockdowns or different behaviors, and to adapt the level of restrictions during the COVID pandemic.

DOMINIC FRIGON: You can certainly use what you see in the wastewater to inform the decision-making on the level of alert that you would have for the next week or the next few weeks, you can actually start planning for your human resources.

DODI: Well, that's pretty useful. How specifically did that work?

CONOR: Well, because of Dominic's work, public health authorities in Quebec could use the wastewater results to know how many testers they would need for the following week, so that they would not be behind the curve in terms of their reaction to the virus.

DOMINIC FRIGON: That's when you have an entire CD signal. And then, if you've changed the resolution of your sampling, you can go all the way to the other end. This is where we understand it and get the better responsiveness, but you can go to the building level when the rapid tests were deployed. But we didn't necessarily have a very large supply of rapid tests, we could actually deploy rapid testing in conjunction with building base sampling of the wastewater.

DODI: Such an excellent use of data. So, what he's saying here is that if he couldn't get enough rapid tests to test the whole population, he could basically batch things and test the population. That is pretty smart!

CONOR: Yes, test where you need to.

DODI: Yeah, but then what about privacy and legal concerns?

CONOR: Well, so technically, Dominic says, when it comes to wastewater, you're talking about sewage, right? So, you put your rubbish out, doesn't belong to you anymore. So legally, he and his team weren't really worried, but just because it's legal doesn't necessarily make it ethical.

DOMINIC FRIGON: If you have, for example, a neighborhood that is mainly a group of a certain ethnicity, then maybe it's a large group whose entire neighborhood it is, that is when maybe you run into problems of stigmatization. So, it's not necessary to be seen on an individual basis. But in a lot of the isolated communities, so in northern Quebec where you have indigenous reserves, information goes very fast, right? And there again, you may actually have certain families that could get stigmatized very quickly.

CONOR: This specific testing was very efficient when finding those who were really vulnerable to a Coronavirus infection. So, one example when the pandemic was at its height, was using this area specific focus, he could pinpoint a dense area of Covid infection down to a single homeless shelter.

DODI: Oh, that is incredible. So, this is a new way of investigating on a viral level. And when Dominic is conducting those tests, is he just looking for COVID? Or is he casting the net wider?

DOMINIC FRIGON: We're looking at SARS-CoV-2 now. Not only do we do we quantify the amount of genome that we have, but we can also sequence the genomes that are present, right? So, we can determine the variants that is in the wastewater and find a number of the different variants that could be in the population. And sometimes we start seeing interesting findings that were not necessarily suspect without the wastewater.

CONOR: So, there's more and it's kind of crazy. Dominic talked about a study from New York that showed multiple mutations in the virus in the wastewater, that strangely weren't showing up in the human infections in the clinical samples.

DODI: I read about this! Yeah, it was awesome.


CONOR: It was spreading outside of the human population and mutating.

DOMINIC FRIGON: And after looking at how some people evolved variants in different animals to see what kind of mutations would occur, and they noticed that the mutation they were seeing in the wastewater, more mutations for sub population of the virus that corresponded to mutations that appeared when the virus was involved in rats, for example, in the lab.

DODI: So, how much does Dominic have to convince people that this wastewater monitoring approach to epidemiology is valid? Or are people like yeah, let's, let's look and let's learn from our wastewater?

CONOR: Well, when it says it's not that much accepted at all in Quebec, in fact, he says two years ago, no one was really talking about getting viral information from wastewater.

DOMINIC FRIGON: The pandemic will have broken these silos in many ways. The public health practitioners, probably like a lot of professions, they're fairly conservative. New data that they don't know enough about, you know, they want the data to be proven. And what is interesting at this point, is some authorities are slow at reacting, but the amount of research that was done in the last two years, is what would typically happen maybe over 10 to 20 years, right? And the number of demonstrations from around the world, at this point, is probably over 10-20 years.

KATA FARKAS: I really hope that it won't just die off when COVID would be less of a problem as the system already exists because we built all this surveillance for COVID.

DODI: Oh, here we have a new voice. Who's this?

CONOR: This is Dr. Kata Farkas...

KATA FARKAS: I am an environmental virologist, and my main research focus is waterborne viruses.

CONOR: In the theme of water, we go back over the pond to Bangor University in Wales and Kata's project aims to describe the fate and behavior of wastewater derived enteric viruses and use that to improve our current risk assessments in water.

KATA FARKAS: So, those viruses that are very resistant in the environment, they can stay infectious for very long, and they can cause illness if you bathe in the water or drink the water and so on. And these are usually like diarrhea, diseases, vomiting and all that. And actually, how these viruses got into the environment, they actually do that via wastewater.

CONOR: These viruses are transmitted via the fecal or oral route, and they're found in feces of an infected person.

KATA FARKAS: In really high concentrations.

DODI: I've heard of this. Is that what's called a norovirus?

CONOR: Yeah, that is one of them. Exactly.

KATA FARKAS: If you are infected with norovirus, just one gramme of your stool have enough viruses to infect each and every human being on the planet. Huge virus numbers we are talking about. They go down the toilet, then to the sewers, down to the wastewater treatment plants. And even during the different treatment processes, they are really resistant and unfortunately, they can be discharged into the water environment. And then if you use that contaminated water, you might get sick. And even they accumulate in shellfish like oysters, and if you eat raw, and they are coming from an area that's contaminated, you'll get sick. Or if you use that wastewater for irrigation, you might get sick, too. So, this was my main focus, and as you can understand, a huge aspect of it is seeing what's in the wastewater and whether these viruses are in the wastewater.

DODI: I can imagine a lot of people might normally think of this as a problem in lower- and middle-income countries in what we call the global south. Or maybe they associate all of this with going on holiday when travelling in the tropics, you know, whenever you go to India, you've got to have that special vaccination card. But I get the sense that this is actually a real problem everywhere. Is that right?

CONOR: Yes, that's absolutely right. And it's a problem driven by urbanization rather than poverty or anything like that.

KATA FARKAS: The more people gather, the more wastewater we produce, the more of that is going into the environment. It's a problem in the UK, in the European Union, and in the US. So everywhere, it's not like a developing problem, per se, it's really common. It's just more developed countries have more tools, more research, and just more mitigation efforts into it to deal with these situations.

DODI: Okay, okay. Let's step back for just a second. Where did all of this start? Was it John Snow, the birth of epidemiology around that water pump in soho during the cholera epidemic? When did we actually start this discipline of looking at what's in the water?

CONOR: Yeah, not quite far back as that but a good while.

KATA FARKAS: Scientifically speaking, the surveillance of water bodies and wastewater has been going on for decades. The first studies that were comprehensive and really looked into this problem, were I think the 50s and 60s. So, ever since then, we know that there is this issue, and there's something our scientists can do about it. For instance, wastewater-based epidemiology – which is now be used for COVID-19, not just in the UK, but all around the world – we've been using that for poliovirus surveillance for decades again. So, it's not like a completely new tool. We just now have better systems, better processes, and better ways to detect viruses and so on, but the concept is not new. It can be used for certain chemicals or other pathogens, too.

DODI: So as a researcher, what does it typical day look like for Kata? Is she spending her time at sewage outfalls? Pew, stinky! Or processing plants in a lab coat? Do people send her samples? How does she actually process everything? And when she puts wastewater into a monitoring system what does it look like? Just take us to her workplace.

CONOR: Yeah, well, she says that the first thing to know is that her work is made a lot easier by the fact that the water industry, the water supply companies, are on board with her research. And that helps all along the way.

KATA FARKAS: So, they are completely happy with doing something for these projects, if necessary, or get deployed auto samplers are just devices able to take graph samples over the day. So, we would have a good idea on what's going on during the day and during the night. And that helps a lot. So, this is what's happening at the treatment plants., and then we get the samples in, and we process them. And the sample process can be really long and difficult, because there as you can imagine, there's so many things in wastewater, it's not just viruses. It's like everything that's come in from a household really, via the sewers. So, we have to be very careful how we actually extract the viruses out from this material, we leave everything behind that would interfere with later detection.

CONOR: Kata says that during her work, she has to be really careful in how she actually extracts the viruses from the samples.

DODI: I was wondering about that. That's why I was asking about her lab or if she is at sewage plants. I mean, we at Cytiva are really into separation and chromatography. We support protein separation, viral clearance, we do all of that kind of stuff. So, what is the actual process of separating out the viruses and what kind of technologies does Dr. Farkas use?

KATA FARKAS: There are many things that we can do right now. At least In the UK, there are two approaches that are used. We can either add chemicals, and then we can use a centrifuge to spin them down and have a virus pellet at the end. The other route that you can use is ultrafiltration. So, basically you have a membrane that has really, really small pores that are smaller than the virus, then you use some pressure to just push everything through those pores, except the virus. And if there's anything that is bigger than the virus, would just stay on top of the membrane. So, you just get rid of actually the water part of the sample. And then the proteins such as viruses, because viruses are basically big proteins, would stay on top, and then you would have your concentrate.

DODI: So, how long until we have something domestically attached to the wastewater outlet from a home, which might signal that there's something in your house, or your diet, or your poop? I actually was watching a TV show where the talking toilet was telling the character on the TV show it's time to see the doctor.

CONOR: Exactly. Well, yes, people are working on that. There's a couple of crowds funded startups and so on, but Kata says, 'Look, sorry, don't hold your breath', or maybe do.

KATA FARKAS: The issue there is that you can do wastewater surveillance at a community level. There are no restrictions at the moment because there are no ethics around it, because it is at community level. You can't stigmatize people or communities. It's coming from everyone. But as soon as you are able to pinpoint certain people, the ethics concerns would be huge.

DODI: This is cool. And like now I'm know I'm inspired and thinking about other ways that we could use this information in this data.

CONOR: Okay, like?

DODI: Well, coming back to Barcelona, like finding out where are the cocaine capitals of the world. Or seriously, I mean, Bill Gates, you probably read this Connor, he's been pressing the need to prevent the next pandemic, when it comes to antimicrobial resistance. He has set up the global epidemic response and mobilization, so another acronym for us, GERM. So, wastewater monitoring could really play a role in something like that.

CONOR: Well, yes, in fact, Professor Frigon says that you could monitor that by dividing up the city that is being inspected into different neighborhoods, and it could be more specific with the monitoring of viruses.

DOMINIC FRIGON: So yesterday, for example, I was in discussion with somebody interested in providing recommendations as to what antimicrobials should be prescribed by physicians, say for urinary tract infections. They monitor what the infections that they see in the hospital, and with that they provide recommendations. Well, most of the urinary tract infections are acquired in the community. And they're mainly auto inoculations and there's only a few types of resistance that we should be monitoring for. So, we could actually use the wastewater and once again we could be ahead of the curve of the infections that come to the clinic and the kind of resistance that they're seeing in the clinic. So, we could actually be more efficient at the top of antibiotics to prescribe there based on the monitoring of the wastewater.

CONOR: So, it's kind of fun right? We think that this stuff is just flushed away and forgotten.

DODI: Yeah, we forget about it as soon as we flush.

CONOR: How much information, data, and insight that can be generated literally from the stuff that we throw away.

DODI: Just love it.

CONOR: Yeah, what could we find in our normal trash right or recycling and what have you? Our executive producers Andrea Kilin. This podcast is produced with the help of Bethany Grace Armitt-Brewster. Editing, mixing, and music is by Thomas Henley and Banda Produktions. My name is Conor McKechnie.

DODI: And my name is Dodi Axelson. Please make sure you rate us on Spotify, where we are asking you to answer a very short poll under the episode description. If you're not on Spotify, you can find us on a myriad of other podcast platforms, and please do rate us there as well. We'll see you soon when we come back with another episode of Discovery Matters. Thank you for listening.

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