Wastewater sampling: a barometer of Covid-19?
A novel testing method
Statistics during a pandemic can make for grim reading.
Frequent headlines about the number of people diagnosed with Covid-19, as well as the mortality rate from these figures, are bombarding us as the news channels go into overdrive.
Governments around the world are making strong political promises to increase the amount of testing to follow in the footsteps of South Korea.
The nation has been praised for its swift handling of the crisis and managing to ‘flatten the curve’. It immediately began testing hundreds of thousands of asymptomatic people, including at drive-through centres, and combined this with a central tracking app.
In the UK, prime minister Boris Johnson has vowed to increase testing to 25,000 per day. Meanwhile in the US, president Trump claims that over one million Americans have now been tested.
Until more rigorous testing happens, potentially thousands, if not millions worldwide are isolating unnecessarily, leaving gaps in key workforces as countries work through unprecedented lockdowns and face increased admissions to hospitals.
With innovation and manufacturing of test kits accelerating, one area has emerged in the meantime as a potential key indicator of the severity of Covid-19 in a community: wastewater sampling.
Detecting Covid-19 in wastewater before official cases
Scientists at Dutch research centre, KWR Water Research Institute, believe that the screening of wastewater can be used as a tool to measure the virus circulation in a population.
Using a novel early warning system principle microbiologist Prof. Gertjan Medema and colleagues detected material from the coronavirus at a wastewater treatment plant in Amersfoort in early March.
This was before any cases had been reported in the city.
They believe that if the method can be substantiated and validated, this would create a tool that provides “valuable additional information about the spread of the virus in the population”.
The SARS-Cov-2 coronavirus has been detected in human wastewater, although it’s unlikely that this will become a route of transmission.
Speaking in a webinar entitled ‘COVID-19: Significance and impact of the pandemic for the water sector’, the professor said: “In surveying the virus in the sewage and collecting knowledge of the virus in the population, we can monitor what happens as the virus spreads in the population.
“By looking into sewers, we can effectively collect information not only on the most severe symptomatic cases but also contribute information on the asymptomatic cases to get a more complete picture.”
He said it would be possible to create a national map through wastewater surveillance, using data from the monitoring systems to see trends and notify the health authorities.
It is also thought the novel method could indicate a number of virus infections in a population to signal a new outbreak, after a lock down has been lifted.
Safety of wastewater operators from Covid-19
Answering the question of whether there is an increased health risk to wastewater operators, Prof Medema said: “The [Covid-19] virus is not robust in wastewater. The limited evidence we have is that they are not infectious when they are contacted through wastewater.
“The risk is low and standard personal protective equipment (PPE) will be adequate to protect the health workers.”
Discussing whether drinking water remains safe, he added: “Yes. Why can we say that? Because we know that other viruses survive better in sewage and water and are more resistant to disinfection. We have proved that our drinking water supply systems can adequately remove/inactivate these.”
Professor Medema has previously been involved in research looking at substances in urban sewage water, including drugs.
“The water sector can support the health sector as there is a critical need for information.”
He said the current research could enable the water sector to support the health sector as there is a “critical need for information”.
In terms of the timeframe for the testing, the professor said that currently it’s possible to collect samples and return results within five days.
A final note of caution
Co-presenting the webinar, Prof. Rosina Girones, research group leader at the University of Barcelona, said that the group of viruses have a lipid envelope, which is “more fragile – we don’t find these associated with waterborne infections”, she said.
Professor Girones added that if the lipid envelope of the virus is destroyed, then the contamination of the virus is removed.
“Wastewater treatment plants are dealing with a high number of viruses all the time, over the course of the year and they can treat viruses known to be more resistant [than Covid-19].”
There was also caution advised from the speakers during the webinar.
One of the conclusions was that Covid-19 had been detected and can still survive for 14 days in sewage. So it’s important for hospitals and cruise ships, for example, that may be in contact with faecal contaminations.
- A recorded version of the webinar is available to watch on the Watershare website.
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