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This story was originally published on RNZ.co.nz and republished with permission.
Geneticist Neil Gemmell is calling for a system to monitor wastewater for potential Covid-19 clusters and carriers of the disease.
It is part of a national group led by the Institute for Environmental Science and Research that has been awarded a $ 1.65 million grant to begin the research.
University of Otago
Professor Neil Gemmell is part of a national group led by the Institute for Environmental Science and Research, which has been awarded a grant to begin research.
Professor Gemmell spoke with Colin Peacock about how monitoring might work.
He says the results from overseas projects and ESR’s current research have been exciting and have shown that sewage could provide an early warning of cases.
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“One of the really important things about this wastewater detection system is that most of the international studies say that Covid in wastewater predicts our detection of diseases in the population using standard approaches, in about two to three days.
“So if we take [the latest outbreak in] Auckland, for example, … that was detected early because the family recognized that they probably had symptoms similar to Covid, they went and got tested, and from there the group grew slowly. And I think we were very fortunate there, and we owe that family a big thank you for getting tested early.
“But if we had had a Covid sewer system installed, maybe we would have detected that group even earlier. Maybe a day or two earlier, I’m not saying we would have, I’m saying it’s a possibility. And one of what I believe What is most important in this Covid epidemic is early information, so we can take action early. “
“So you’re getting indications that people are carriers of the disease in a population, perhaps asymptomatic, long before they actually feel sick and then get tested for Covid.”
So far, the first studies of wastewater testing have been done retrospectively in places where an outbreak has occurred, including Italy, the Netherlands and Australia. The scientists used wastewater previously collected from those areas and compared the wastewater tests with case data from the same period.
The New Zealand team was able to find the virus in wastewater from the Tahuna sewage treatment plant, from late March and April.
“But perhaps one of the most compelling cases for wastewater use came from an Arizona State University study about a month ago,” Gemmell says.
“What they were doing is that when the college year started in North America, they implemented a sewage detection system at their residential colleges.
“So they had a university there with 300 individuals, and they tested positive on the sewage. And then they went back and used the classic nasal tests … to scan that population of 300 individuals, and they found two asymptomatic cases.
“So their argument was that by using this surveillance approach they prevented a full-blown Covid group from emerging at one of their residential universities.”
Gemmell says that detecting Covid-19 is not an easy task, whether in traditional medical testing stations or in wastewater.
Cecilia Fabiano / AP
Gemmell says that detecting Covid-19 is not an easy task, whether in traditional medical testing stations or in wastewater. (File photo)
“There is actually a lot of work involved in processing wastewater samples, so it’s slow and painstaking work. We don’t have a process to automate that right now, and I don’t think anyone does it internationally. But You are collecting a lot of information from a single sample from many people and that is where the power lies.
“First you have to get a sample, and of course the question is how representative is that sample of the population that you’re analyzing. You have to concentrate that sample, and then you have to extract the RNA, because it is an RNA virus that we are detecting “.
Then chemical reactions are used to amplify the virus by making copies of it, so there is enough to detect.
“There are a lot of things that can go wrong there – you may not get a sample that is representative of the population, you may get different flow rates, stormwater may enter the system, there will be pollutants and other things there, and other things that they’re going to inhibit your test reaction. So it’s pretty complicated, but doable. “
Where in the wastewater system could be sampled and how many samples would it take to cover a group remain important questions.
“The closer you get to a source, the fewer people you have to go back to [test]. It’s kind of like our approach to contact tracing, but at the sewer level, “Gemmell says.
“It’s not a creepy big brother thing, no one is identified through this, it’s just a sample of individuals.
“So, let’s say … you’re doing it in an airport for a certain period of time and you get a detection there, it would be as if we had a detection in a site that we had visited with our Covid app. Maybe that detection in the sewage would give an alert saying that there has been a detection present in that location where you were, and then the question is should you go and get tested if you show symptoms? “
The Dunedin tests have given the team an opportunity to begin exploring the question of sample points, he says.
“Here in Dunedin we have a major treatment center that has been effectively covering 100,000 people. But there are different sinks, collection points, and in Dunedin we have some of those and we are working to try to find out how many.
“So those kinds of collection points … could be areas where you’d get a representation of a few thousand individuals, so it’s not a fine scale. But in terms of mass screening a population, let’s say you’re doing One thousand, ten thousand people, and you don’t get anything on a regular basis, that gives us some confidence that we can go about our daily lives safe from Covid-19.
“If we get a detection, that could trigger an alert system, then we go into the standard screening procedures of the Ministry of Health where we ask people who have been in that area to get tested. It’s a little more targeted approach.” .
He is eager to see the investigation move to the next phase.
“At this stage, it’s like trying and seeing how the scenario works: If we were to set up a massive system and then find out that it really doesn’t work the way we hope, it would be a mistake. We’re trying to find some exemplary situations where we can test to see if this works.
“And of course there is relatively little Covid in New Zealand, so the best places to test are in managed isolation units. So if that works, we can look to extend it to a much larger network.
“But I think a sample every other day would not be a bad place to start, from key locations. In New Zealand, I think some of those key locations are; our airports, most of the cases that we receive are imported cases; our systems port facilities; our managed isolation units. They would be potential focus locations, and then maybe a little wider network outside of those. “
This story was originally published on RNZ.co.nz and republished with permission.
