A new research paper by Professor Richard Quilliam of the University of Stirling, UK, says that the waste water system could pose a transmission risk.

The response to the global pandemic has focused upon preventing person-to-person transmission. Now, experts have stressed that the virus could also be spread in wastewater.

A new paper by Professor Richard Quilliam of the University of Stirling, UK, warns that the sewerage system could pose a transmission risk. Writing in the journal Environment International, Professor Quilliam and colleagues from Stirling’s Faculty of Natural Sciences are calling for “an investment of resources” to investigate their concerns.

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

The paper presents the example of the SARS outbreak in 2002-03, when the SARS-CoV1 virus (closely linked to the SARS-CoV2 virus that causes Covid-19) was detected in sewage discharged by two hospitals in China. Professor Quilliam highlighted that, as most Covid-19 patients are asymptomatic or experience just mild symptoms and remain at home, and not in hospitals, there is significant risk of “widespread” distribution through sewers.

The authors added that the structural makeup of the virus suggests that it will behave differently in aqueous environments. 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.

Can Covid-19 spread through wastewater

On the risk of human exposure, the authors said: “The transport of coronaviruses in water could increase the potential for the virus to become aerosolized, 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.”

Risk could be further increased in parts of the world with high levels of open defecation, or where safely managed sanitation systems are limited and waterways are used as both open sewers and sources of water for domestic purposes. —Source: University of Stirling