In this story episode of The Outfall, we talk to two researchers on the front lines of using wastewater to analyze the epidemiology of a community. Wastewater surveillance for the Coronavirus has huge potential. Data suggests that each person infected will excrete millions, if not billions of viral genomes into the wastewater per day. We learn more about why this research is so important, what is going on now, and what the future of this research looks like.
By looking at sewage, it’s actually a leading indicator of pandemics as opposed to death, which is the lagging indicator of pandemics.
Dr. Ian Pepper
Thanks again to our guests:
- Dr. Sean Norman, Associate professor in the Department of Environmental Health Sciences at the University of South Carolina. Learn more here.
- Dr. Ian Pepper, Environmental Microbiologists at the University of Arizona. Learn more here.
Transcript
Robert Osborne:
This disease had not been seen in Israel since 1988. Suddenly alarms were going off in 2013 with the Israeli Ministry of Health. They confirmed the presence of it. Polio had been detected. However, the real story here is not polio, but how it had been detected. Israel had set up a wastewater surveillance system in 1989 involving collecting wastewater samples from sewer collection systems and plants on a weekly basis. They soon figured out that this strain was from Pakistan, and they were able to vaccinate this certain area. Fast forward to 2020. Now researchers from around the world are focused on another virus and are racing to collect wastewater samples. In this episode of The Outfall, we talk to two researchers on this frontline. Let’s start first with why this research is so important.
Dr. Sean Norman:
What we’re faced with right now is the inability to do a lot of individual testing on people, so we don’t know the true abundance of the virus in the community. Taking an approach like this is not just my group doing this, there are other groups around the world that are starting to do this. We are starting to call this wastewater epidemiology, and that is using wastewater to analyze or to look at the epidemiology of a community. So if you can’t go in and individually test an entire population of people, there’s really not necessarily a better way than using sewage because a sewer shed is collecting the information from a population of people throughout a community.
Robert Osborne:
This is Dr. Sean Norman, associate professor in the Department of Environmental Health Sciences at the University of South Carolina. He has spent the last 10 years looking at the antibiotic resistance bacteria cycle through the wastewater treatment plans. Now, this was before he got a call from the CDC several months ago to shift his lab focus to the Coronavirus.
Dr. Sean Norman:
Make some assumptions based on the overall abundance of the virus in the community. Now, if we can do that and we can get a decent baseline information that is able to track the number of cases that are occurring, then we actually start being able to model those data and develop predictive models to then say, okay. Well, we’re starting to see an uptick in the abundance of the virus in raw sewage that might signal a second wave of the virus hitting the community. With that information then policymakers, public health officials, healthcare workers can all be geared up for another wave coming, and maybe policymakers decide that we might want to reestablish social isolation rules a little bit more.
Robert Osborne:
Wastewater surveillance for Coronavirus has a huge potential. Data suggests that each person infected will excrete millions, if not billions of viral genomes into the wastewater per day. This can start in fact, on the third day of infection before any symptoms develop.
Dr. Ian Pepper:
By looking at sewage, it’s actually a leading indicator of pandemics as opposed to death, which is the lagging indicator of pandemics. So in other words, you find in first in the sewage, subsequently, people die. That takes a bit of time so that’s the lagging indicator. Some of the other aspects that I think are interesting is that it will detect viruses shared by individuals who are infected but asymptomatic. So I think that’s a huge advantage because I believe, and it’s really just coming to light now, that the number of people really infected by the virus in the United… Well, worldwide. Numbers are far greater than just the number of people that show up with symptoms. So this is really a good indicator.
Robert Osborne:
This is Dr. Ian Pepper, an environmental microbiologist at the University of Arizona. So far, they’ve been analyzing samples from 15 different wastewater treatment plants from across the country.
Dr. Ian Pepper:
We’d been taking a lot of samples here at a wastewater treatment plant close to us, here in Tucson, getting two samples a week. We haven’t analyzed them all yet, but we have been able to show the samples that we’ve looked at, first showing an increase in concentration and subsequently now they are showing a decrease. And I’m thinking that we may be past the worst of it here in Tucson. I think yesterday there was only 10 additional cases which is, as you know, that’s excellent.
Robert Osborne:
Dr. Norman is also analyzing a number of wastewater treatment plants. He’s got about eight in South Carolina, two in Texas and one in California. They can analyze the samples in less than 24 hours, but it involves a lot of work.
Dr. Sean Norman:
So really where our time is spent mostly is processing, doing our pre-processing of the samples, so that we can get material to then extract the nucleic acids, the DNA and RNA out of, so we can have the RNA to analyze for the virus. So we go from a leader of raw sewage, concentrated down into 200 mils, then down further into 400 microliters. So that concentration step is really the time consuming part. So we’re centrifuging the samples first, then we separate out any kind of pelleted material, like any organics or any larger particles that might be in the material. We pellet that out, save the pellet, off to the side. Then we take the supernate and we [inaudible 00:05:59] that through ultra filters that have a molecular weight cutoff of about 30 kilodaltons, so we’re capturing all the viruses that could be in there. Then we do a nucleic acid extraction from the pellet as well as the concentrated filtered material.
Robert Osborne:
Each sample of wastewater is a unique snapshot of that community. Understanding variables in that snapshot will be important.
Dr. Sean Norman:
What variables do we need from the utilities to make our models more accurate? Total suspended [inaudible 00:06:36] would be one. We would want to know if there’s a rain event, not a rain event, because that could affect flow. We need to look at the population of people being served by the sewer shed. How many domestic accounts versus industrial accounts? There are a lot of different variables that we’ll start plugging into the model and see how each of these variables influence the model.
Robert Osborne:
So how many Coronavirus genes survive the journey from a toilet to a wastewater treatment plant? We asked Dr. Pepper.
Dr. Ian Pepper:
We know from the work we did back in that paper in 2009, Coronavirus, or the one we were studying then, could survive two to four days in wastewater. So the most likely place you would find the virus if it’s there, would be in the raw sewage, so we’ve been asking people to give us samples of the rural sewage and after secondary treatment. And so far we found in some cases, we find it in the raw sewage, we don’t find it after secondary treatment. However, as all good research does that leads to yet another question that we need to research. And that is, is the virus becoming inactivated or is it merely partitioned into the solid phase? In which case it would ultimately end up potentially in biosolids after anaerobic digestion. Done a lot of work with biosolids over many years, and we know from the calls that we’re getting that people that are land applying biosolids are getting hammered with questions about the potential for biosolids as a vehicle for exposure to the virus.
Dr. Ian Pepper:
It’s extremely unlikely because it’s unlikely to survive anaerobic digestion. And in another part of the research that we’re doing, that’s one of the things we want to do, is to look at the effects of anaerobic digestion on the virus using miniature anaerobic chambers with sludge that is anaerobic to digest it. So we spike the sample, let it digest, sacrifice the samples another time, and typically at wastewater treatment plants anaerobic digestion goes for 21 days. We’ve done that, surrogates for the Ebola virus, because believe it or not, we do like our students, so we use surrogates. And that was very successful and showed that Ebola did not survive the anaerobic digestion. And we’re very confident that Coronavirus won’t. But of course, even if you’re 99.9% sure of that, the 0.1% will eat you alive. So you have to do the study to show it.
Robert Osborne:
In the coming months, researchers will have their hands full with sampling, testing, dialing in on the right assumptions to turn this data into models that could become a frontline battle-hardened public health tool.
Dr. Sean Norman:
I’m most curious about seeing if we can adopt this into a model to be able to assess the true percentage of the population that’s infected by the virus. That to me is the golden ticket for the work that we’re doing. Between that, if we can do that, then we can make it a predictive model, then it becomes an applied public health tool that might be able to be adopted by policymakers.
Robert Osborne:
I’d like to thank Dr. Ian Pepper and Dr. Sean Norman for giving us just a glimpse into the behind the scenes world of this real-time research as it all comes together. Also big thank you to David and Amy. Since the pandemic started we’ve been getting together virtually most every Thursday night. It’s a great time after the kids and animals are asleep, bringing guests on and just generally reconnecting. One thing I love about putting these shows on is it always starts with some fragment of an idea. Someone mentioned something, and then we follow our curiosity.
David Ladner:
Because I do remember Amy brought it up. She was really excited about-
Amy Anderson:
Yes.
Robert Osborne:
Oh, you got an email.
David Ladner:
Well, tell it. Tell us the story, Amy. What was the deal that first got you clued in that people were doing this?
Amy Anderson:
A member of this pretreatment listserv that’s across the US and someone had posited the question, “Hey, I got this weird solicitation from this company called Biobot, that’s interested in sampling sewage. Surely this is a hoax and they’re just trying to get my information and capitalize on this pandemic.” So of course I immediately checked it out and it seemed legitimate, and they were soliciting sewage samples. So I sent an inquiry and emailed back right away, and ever since then it seems like we’ve seen stories popping up of the usefulness of sewage surveillance as a tool for tracking the spread of the disease, even before you get an idea of it in the community. And actually having a better idea of how it is spreading in the community.
David Ladner:
Who knew that with all the spam emails out there the one email that asked for poop samples is legitimate?
Robert Osborne:
Well then how did that lead to Dr. Pepper? Was that… That was you then wasn’t it David?
David Ladner:
Well, I guess I started looking around because after Amy had brought it up I started noticing things on Twitter that people were posting, and a lot of other professors of environmental engineering. So a few colleagues of mine were talking about some studies that were happening. So I just started looking around at what was being done and where, and I noticed that there was this study at University of Arizona, and I didn’t know Ian Pepper personally, I hadn’t met him or anything. But I did remember taking a class using his book, I think it was Environmental Microbiology. And so I figured that could be at least some kind of a connection that would allow me to contact him and ask if we could interview him.
Robert Osborne:
And then somehow I think we passed around a newspaper article about Dr. Sean Norman’s work he was doing with the city of Columbia and that sort of connected us with him. If you are interested in this topic more, we’ve posted some more resources on our website. Thanks again for joining us, and we’ll see you again next time.
