Coronavirus: How water flushed down our toilets can help track COVID-19? Know all about sewage testing

Since the onset of novel coronavirus, scientists have gone out of their way to develop tools to detect the SARs-COV-2 virus. Sewage testing and surveillance has gained much momentum in recent times and is said to be an effective way to track the spread of the virus and identify viral hotspots in communities. In a bid to detect a COVID-19 outbreak in largely populated areas, several countries including US, Australia and India, are now using this approach. Therefore, it is important to understand what wastewater surveillance means, how it works and why it has become integral to the management of COVID-19 crisis.

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Sewage testing has proved to be an effective and quick way to monitor and track the presence of viruses, bacteria and other pathogens in the wastewater.

Wastewater surveillance therefore is the process of examining sewage water or the water that we flush down our toilets regularly so as to look out for contaminants and viral particles. While viruses cannot do without its host cell, the technique involves looking out for the genetic material or the RNA fragments of the virus, which in case of COVID-19 is the SARS-CoV-2 virus, in the wastewater.

The use of sewage surveillance was first recognized by researchers at Yale University in the 1960s. This was when the scientists were trying to analyze and assess the effectiveness of the polio vaccination. Another study conducted by Israeli researchers found polio virus in the sewage 9 days prior to the identification of the first polio case.

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Those infected with COVID-19 have virus fragments that they shed or excrete in the form of bodily fluids or faeces about two to three days after infection. Once flushed into the sewage system, the virus slowly disintegrates, leaving behind fragments of the genetic material or the RNA. The fragments are then filtered and isolated from the wastewater to track the presence of virus.

Detecting the SARs-COV-2 virus through wastewater surveillance is said to be a safe process. Given that the viral fragments cannot survive without the hosts and since it is broken down by all the chemicals in the wastewater and through the sewage treatment process, the fragments may no longer be infectious but detectable.

As far as the effectiveness is concerned, a US study estimated that wastewater surveillance could detect one coronavirus infection for every 100 people to a minimum. The best it could do is detect up to one infection per two million people.

While individual testing through rapid antigen or RT PCR testing remains the most effective way to diagnose COVID-19, wastewater sampling can help monitor and track the spread of the virus at a larger scale. Since testing everyone in a community is impossible, using wastewater surveillance helps gather efficient community samples from communities that lack timely COVID-19 testing facilities. It also helps obtain information regarding an epidemic situation of infectious diseases like coronavirus.