Scientists buck trend to warn sewerage could pose a Covid-19 transmission risk

Biologists at the University of Stirling have warned that the sewerage system could pose a transmission risk for Covid-19. The claim challenges the widely held understanding that the SARS CoV 2 virus that causes Covid 19 does not remain viable in sewerage long enough to present a serious risk.

Professor Richard Quilliam and colleagues from Stirling's Faculty of Natural Sciences raised their concern in a peer-reviewed article in the journal Environment International.

They have cited other findings reported in March by Chinese researchers that show genetic material (nucleic acid) from the virus can be found in human faeces up to 33 days after the patient had tested negative for respiratory symptoms of Covid-19. But those scientists highlight that "determining whether a virus is viable using nucleic acid detection is difficult." And they go on to point out that "No cases of transmission via the faecal–oral route have yet been reported for SARS-CoV-2."

And Quilliam's team cite earlier research from the SARS outbreak in 2002-3, that found that material from SARS-CoV-1 (closely linked to the Covid-19 strain) was detected in sewage discharged by two Chinese hospitals. The researchers behind that study said " no live SARS-CoV detected in the sewage." from those hospitals.

There is currently limited information on the environmental persistence of Covid-19, but other coronaviruses can remain viable in sewage for up to 14 days, depending on the environmental conditions.

On the risk of human exposure, Quilliam's team said: "The transport of coronaviruses in water could increase the potential for the virus to become aerosolised, particularly during the pumping of wastewater through sewerage systems, at the wastewater treatment works, and during its discharge and the subsequent transport through the catchment drainage network.

"Atmospheric loading of coronaviruses in water droplets from wastewater is poorly understood but could provide a more direct respiratory route for human exposure, particularly at sewage pumping stations, wastewater treatment works and near waterways that are receiving wastewater."