Coronavirus: Experts warn potential for Covid-19 to spread through sewage ‘must not be neglected’ by researchers

The potential for coronavirus to spread through sewage “must not be neglected” in efforts to contain the Covid-19 pandemic, environmental biologists have warned.

Although attempts to slow the spread of the virus have mainly focused on preventing human-to-human transmission, experts from the University of Stirling have now warned more research is needed on how Covid-19 could spread in wastewater.

Researchers suggested in April that analysing sewage could provide an effective early warning system for outbreaks after wastewater sampling at five sewage planets in Paris, France, revealed a pattern of coronavirus concentration which coincided with outbreaks of cases.

On Tuesday, a separate research team at Bangor University said analysing sewage could help health officials to predict a second peak of coronavirus in the UK up to two weeks before people become symptomatic.

Now, Professor Richard Quilliam, from the University of Stirling, has warned in a paper for Environment International that the sewage system itself could also pose a transmission risk for the virus.

“We know that Covid-19 is spread through droplets from coughs and sneezes, or via objects or materials that carry infection,” Professor Quilliam said.

“However, it has recently been confirmed that the virus can also be found in human faeces - up to 33 days after the patient has tested negative for the respiratory symptoms of Covid-19.”

He added: “It is not yet known whether the virus can be transmitted via the faecal-oral route, however, we know that viral shedding from the digestive system can last longer than shedding from the respiratory tract.

“Therefore, this could be an important - but as yet unquantified - pathway for increased exposure.”

Professor Quilliam and his colleagues from the University of Stirling’s Faculty of Natural Sciences have called for “an investment of resources” to investigate the issue.

He said there was a significant risk of “widespread” distribution of the coronavirus through sewers because most patients are either asymptomatic or experience only mild symptoms and remain at home.

The research team said a lack of testing had made it “difficult” to predict the scale of the potential spread and the implications of the virus arriving at wastewater treatment works.

Their findings also suggested there could be greater risk for parts of the world with high levels of open defecation and areas which do not have safely managed sanitation systems.

“Such settings are commonly accompanied by poorly resourced and fragile healthcare systems, thus amplifying both exposure risk and potential mortality,” the authors said.

The paper was authored by Professor Quilliam, alongside Professor Manfred Weidmann, Dr Vanessa Moresco, Heather Purshouse, Dr Zoe O'Hara, and Dr David Oliver.