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Can Wastewater Testing tell us more about COVID-19?

July 06, 2020 08:31 IST
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'Wastewater containing excreted material can tell us how a community is doing in a particular area pertaining to any epidemic, pandemic, and other bacterial and viral diseases.' 

Photograph: Parivartan Sharma/Reuters

For the first time in India, a study conducted by a group of scientists at the Indian Institute of Technology-Gandhinagar along with the Gujarat Biotechnology Research Centre and the Gujarat Pollution Control Board has detected the genetic material of the SARS-CoV-2 in wastewater.

The samples of wastewater were collected on May 8 and May 27 from the Old Pirana Waste Water Treatment Plant in Ahmedabad.

Manish Kumar, assistant professor, earth sciences, at IIT-Gandhinagar, who led the study, tells Shobha Warrier/ how this breakthrough can pave the way for using wastewater-based epidemiology for real-time surveillance of COVID-19.

One of the first studies on wastewater was done in Italy and the study found that the coronavirus came to Italy in December 2019.
Till then it was believed that the virus came there much later.
Did you see any startling revelations when you conducted wastewater studies in Ahmedabad?

The first question in front of us was whether we would be able to detect the SARS virus in wastewater or not.

The second question was, whether the presence of the genetic copy of the virus will correlate with the number of COVID-19 cases in the area.

Our study could answer both questions. We found that if we keep the conditions constant like, how much waste is collected, whether or not wastes are leaked on the way, diurnal variations and others, the genetic loadings of SARS-CoV-2 is detectable in the wastewater.

And when present, and the loading corresponded to COVID-19 variations.

It shows wastewater-based epidemiology can be used to understand monthly, weekly, or daily variations of overall conditions of COVID-19 cases in a given community. We will be able to know if the situation is worsening or improving. 

Another important implication is that we can give early warnings on pandemics through wastewater surveillance.

That is because a symptomatic patient of COVID-19 will shred genetic material of the virus at least 72 hours before any symptoms being noted by the given individual.

Even asymptomatic patients also shed viral RNA through excretion.

In order to give an early warning, don't you have to do testing almost every day?

Yes, at least, weekly tests are necessary.

Although in my opinion, we need to test once in three days, which is not very difficult because one water sample will cost us only what is equivalent to any individual's sample cost.

On the other hand, wastewater can give us an idea about the community of various sizes.

Can we say wastewater testing is the best way to tackle any pandemic or epidemic as you get early signals?

Yes. What are the first tests doctors ask us to do when we are sick? Don't they include urine and stool test?

Likewise, wastewater containing excreted material can tell us how a community is doing in a particular area pertaining to any epidemic, pandemic, and other bacterial and viral diseases.

In Italy, they found that the origin of the virus dated back to December 2019. Does that mean you can find out when exactly the virus originated?

No. Only if we have taken the samples in a particular period and preserved them to test later on, we will be able to know whether the virus was present at that particular time or not.

If there is no sample, you will not know about its presence.

You will be surprised to know that another wastewater sample test done in Barcelona says the SARS-CoV-2 was present in the city as far back as in March 2019!

It means the virus was there much before it was reported in Wuhan in November 2019, and in Italy in December 2019.

They could identify the virus in the March 12, 2019 sample because they had the sample of that time period with them in the labs.

Does that mean people calling the novel coronavirus, a Wuhan virus and accusing China of spreading the pandemic, is not right?

I still suspect China as the originating place of the virus because of the fact that SARS-CoV-2 has its transmission through some sort of eating behaviour of humans of its intermediate hosts like pangolin or fish carrying the zoonotic viruses.

But the primary reservoir is reported to be bats. These species are frequently used as food items in China.

The Barcelona case seems to me more related to business or personal trips taken by infected people.

Just because we identified the virus in Barcelona does not mean that it originated there. Globalisation is the key here, and Spain is one of the most visited places in the world.

It is said Wastewater Based Epidemiology is one of the best ways to detect epidemics. But all over the world, only a few countries like The Netherlands, the US, Australia and France are doing such tests for the coronavirus.
Why is it that it is not done everywhere?

First, testing for the viruses in wastewater was not an area that was given adequate importance or focus till now. Only when the pandemic came that many people have started looking into this field.

You need a lot of expertise to do these tests. One fine day you cannot become an epidemiologist or a hydrologist. It is a fact that there is only a very small community of experts in the world who are working in this field.

In my case, I have been working on antibiotics, antibiotic resistant bacteria, antibiotic resistant genes, and virus detection in the wastewater since 2016 onwards.

As I was exposed to virus-related analyses and research and have published my work on enveloped viruses in Guwahati wastewater in Science of the Total Environment, I knew I could try my hands on the novel coronavirus.

Also, you need a lot of courage to do wastewater testing, as you are not fully aware of its infectivity, and are dealing with a novel virus strain never known before.

In fact, nobody likes to touch the wastewater sample that has a virus in it.

Even now, not many people would like to work in this field unless they are clear about infectivity and transmission.

But this is a field that can help countries detect diseases early.

Yes. We could establish the proof of the concept through wastewater studies. Today countries like Italy, Spain, the USA, Australia, Japan are leading.

If we do these tests at regular intervals in situations like these, we would also be able to notify the authorities to prepare for any condition and can also inform common people if the situation is improving.

Such monitoring can help us give early forecast like we give on weather, or tsunami and earthquake warnings.

Using Wastewater Based Epidemiology surveillance, we can prepare ourselves for pandemics, and thus minimise the spread and save lives.

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Related News: Parivartan, Reuters