Can be the traces of COVID-19 detected in wastewater?

Eawag (Swiss Federal Institute of Aquatic Science and Technology), in its recent article pointed out that traces of COVID-19 can be detected in wastewater.

The novel coronavirus has been successfully detected in wastewater in samples collected at an early stage of the outbreak. The aim is to develop a system which could warn of a resurgence of cases earlier than clinical diagnostic tests.

“Detection and quantification of SARS-CoV-2 in wastewater” – research projects on this scale generally take several years, but thanks to major efforts, a group of scientists could reach valuable results during the early stage of their project. Initial wastewater samples have been analysed from the period at the end of February when the first cases of infection were recorded in Switzerland. The researchers managed to detect the novel coronavirus in all the samples analysed. The researchers did not expect this result either:

“We didn’t expect that we’d already be able to measure a signal in wastewater …., with only six known cases.”

The successful detection of low viral concentrations at an early stage of the outbreak means that it should be possible, retrospectively, to trace the rise of the COVID-19 curve. The scientists were able to roughly trace the increase in SARS-CoV-2 concentrations in wastewater between March and April. They estimation is that this represents a 10- to 100-fold rise.

The main aim of the project is to develop an early warning system. According to the hope of researchers, the resurgence of infections during the lockdown exit period could probably be detected earlier than with diagnostic tests – about a week earlier. 

“Wastewater doesn’t lie, and it reflects what is excreted by the public within a few hours.” 

Despite the group’s initial successes, the method now needs to be further optimized, due to a few high uncertainty factors. Only when these can also be reduced will it be possible to draw robust conclusions about viral concentrations in the original samples.

Coronavirus unlikely to spread via water or wastewater...

While genetic material from the novel coronavirus can be detected in wastewater, there is no evidence at present to suggest that the pathogen spreads via water or wastewater. 

Sampling on the wasteawater treatment plant Werdhölzli in Zurich.
(Photo: Eawag, Andri Bryner)

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