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Friday, June 05, 2020

Explained: Why it is important to determine whether Covid-19 can spread through sewage

Researchers have detected the coronavirus in the stool of both symptomatic and asymptomatic patients. This information has helped them identify the virus in untreated wastewater.

By: Explained Desk | New Delhi | Updated: May 16, 2020 1:43:24 pm
Explained: Why it's important to determine whether Covid-19 can spread through sewage There is also no evidence yet to prove the virus can be transmitted through the faecal-oral route. (Source: Getty Images)

Researchers in Australia are developing a technology to help track the transmission of the novel coronavirus through waterwater. The early warning surveillance system will identify the virus by its genetic material, or the RNA (Ribonucleic Acid).

The researchers, from the University of Queensland and Australia’s national science agency CSIRO, were able to prove the presence of the coronavirus in untreated sewage water in Queensland after taking samples from one suburban pumping station and two wastewater treatment plants (WWTP). They analysed the wastewater samples using RT-PCR tests, which helps identify gene fragments of the SARS-CoV-2 virus. This is also the method used by hospitals to test for the virus in human samples.

Their paper has been accepted for publication in the journal Science of the Total Environment.

Transmission of Covid-19 through wastewater: the research

The premise of the research was that patients infected by Covid-19 shed the virus in their stool. In fact, the virus had already been detected in the stool of both symptomatic and asymptomatic patients. This information helped identify the virus in untreated sewage.

As water is not the primary route of transmission for coronaviruses, it remains unclear whether these virus particles are infectious. There is also no evidence yet to prove the virus can be transmitted through the faecal-oral route.

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According to Netherlands-based KWR Watercycle Research Institute, the RNA of the virus can only be stable in wastewater if it is protected by its protein coat, which otherwise would rapidly decompose. It also stated that the presence of the virus in wastewater seemed unlikely to infect people.

“We currently know too little about the possible infectious activity of coronavirus (SARS-CoV-2) particles in sewage water, but from the information that we have this far it does not seem very likely that coronavirus particles in wastewater can infect people,” the institute said on its website.

Researchers from the University of Stirling, UK, have also warned in the journal Environment International that the virus could be found in human faeces — “up to 33 days after the patient has tested negative for the respiratory symptoms of Covid-19”.

Another study in 2003 found the SARS virus remained infectious in stool at 20 degrees Celsius for a period of 4-5 days.

So, why is this research important?

This method of wastewater-based epidemiology (WBE) may be a useful approach to determine the approximate number of people who might be infected by the virus in an area. This is especially because several individuals do not show symptoms, making it harder to detect infectious patients.

The presence of the virus in wastewater could also signal trends in disease transmission, that is, if its spread is increasing or decreasing. However, researchers say establishing quantitative predictions using untreated samples of wastewater would be one of the “biggest challenges”.

These trends, if discovered, could help decision makers increase testing more aggressively in particular areas.

On Tuesday, The Guardian reported that the testing method detailed by the researchers would be rolled out by Victoria’s health department and that regular testing of sewage water may start in June.

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