UQ, CSIRO, say poo could be an early warning system for tracking COVID-19

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Researchers across the globe have been tracing the spread of the coronavirus through waste water and sewage and several scientific studies have picked up the clear presence of COVID-19 in patients' stools. Testing human sewage could now become a key way of tracking the pandemic's spread, and a precious early warning system for a feared second wave, said researchers from the University of Queensland and CSIRO who are developing an early warning system to track COVID-19 in the community through tracing the presence of the SARS-CoV-2 RNA in raw sewage.

Coronavirus and the gut

SARS-CoV-2 gains entry into human cells by latching onto ACE2 protein receptors, which are found on certain cells’ surfaces. Around 2% of the cells lining the respiratory tract have ACE2 receptors, while they’re also found in the cells lining the blood vessels. But the greatest numbers of ACE2 receptors are actually found in the cells lining the gut (oesophagus, stomach, small bowel and rectum). Around 30% of cells lining the ileum contain ACE2 receptors.

Clinicians have detected coronavirus in tissue taken from the lining of the gut through routine procedures such as endoscopy and colonoscopy, where we use cameras to look inside the body. They found abundant ACE2 receptors in those tissue samples.

Gastrointestinal symptoms including diarrhoea, vomiting and abdominal pain are not unheard of in people who contract coronavirus. While some researchers have proposed alternative explanations, it’s likely people with COVID-19 experience gastrointestinal symptoms because the virus directly attacks the gut tissue through ACE2 receptors.

Researchers worldwide have found genetic traces of SARS-CoV-2 in waste water in toilets, sewers and sewage farms, and now UQ and CSIRO researchers have found RNA fragments of SARS-CoV2 in untreated sewage which would have been shed in the waste water stream by COVID-19 infected people. While the presence of the virus in faeces does not mean that it can be transmitted through them.

Call for an early warning network

For SARS-CoV-2, waste water studies in several countries are still at an early stage. But some scientists are enthusiastic about their potential.

A proof of concept study has been completed using wastewater samples from two wastewater treatment plants in South East Queensland, representing populations living in the Brisbane region. Director of UQ's Queensland Alliance for Environmental Health Sciences Professor Kevin Thomas said the validated method built on work by research groups in the US and Netherlands, including work by Willemijn Lodder and Ana Maria de Roda Husman from the Dutch Centre for Infectious Diseases Control who recently published in a paper in The Lancet

"This is a major development that enables surveillance of the spread of the virus through Australian communities," Professor Thomas said.

"It could be used as an early warning tool for pandemic surveillance," said Dr Warish Ahmed from CSIRO. Having found the virus in waste water in Queensland, he said it could also be a key indicator to show if lockdown and other measures were working.

"Access to this type of data could underpin a surveillance program to identify areas where there is evidence of Covid-19 outbreaks, without requiring testing of all individuals," Dr Warish said.

He said although it was a "cost effective way of tracking community-level infection", he warned that it should be used "in combination with other measures, such as the testing of individuals."

CSIRO Chief Executive Dr. Larry Marshall said the testing would help Australia manage COVID-19. "The hope is eventually we will be able to not just detect the geographic regions where COVID-19 is present, but also the approximate number of people infected, without testing every individual in a location. This will give the public a better sense of how well we are containing this pandemic," he said.

'Precisely followed deaths'

French virologist Professor Vincent Marechal of the Sorbonne university in Paris said it could even allow experts to "track the virus”. In a study of waste water in Paris, which has yet to be validated by other scientists, Marechal and his team found that the rise in levels of genetic material from the virus in water "followed precisely the number of (coronavirus) deaths". Marechal is now call for a national waste water warning system in France which might help "anticipate a second wave" of the virus.

Given the large number of coronavirus cases that have little or no symptoms, waste water testing could signal the presence of the virus even before the first cases are clinically confirmed in areas untouched by the epidemic or where it has ebbed.

"That would allow barrier measures to be put place and give us time, a key element with this epidemic," Marechal added.

Such a system has already worked against other viruses. In a study published in 2018, researchers showed how polio being detected in waste water in Israel in 2013 gave time for a vaccination campaign to be launched, which meant no child was paralysed by the disease.

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