SARS-CoV-2 in Paris wastewaters

SARS-CoV-2 in Paris wastewaters. Jefferson T, Heneghan C.

Published on July 2, 2020

Reference Wurtzer S, Marechal V, Mouchel J-M, Maday Y, Teyssou R, Richard E, et al. Evaluation of lockdown impact on SARS-CoV-2 dynamics through viral genome quantification in Paris wastewaters. medRxiv. 2020
Study type
Country France
Setting Community
Funding Details Eau de Paris 2020 Research grant
Transmission mode Orofecal

Bottom Line

Quantitative monitoring of SARS-CoV-2 genomes in wastewaters may enhance surveillance intelligence of circulation at local or regional scales.

Evidence Summary

The increase of genome units in raw wastewaters accurately followed the increase of human COVID-19 cases observed at the regional level. The shape of the concentration curve was similar to that of the disease at the regional level, with an 8-day time lag.  

Viral genomes could be detected before the beginning of the exponential growth of the epidemic. As importantly, a marked decrease in the quantities of genomes units was observed concomitantly with the reduction in the number of new COVID-19 cases which was an expected consequence of the lockdown.

Source: Evaluation of lockdown impact on SARS-CoV-2 dynamics through viral genome quantification in Paris wastewaters. medRxiv. 2020:2020.04.12.20062679.

What did they do?

The study was designed to test the assumption that SARS-CoV-2 genomes in wastewaters correlate with the number of symptomatic or non-symptomatic carriers. The authors performed a time-course  quantitative analysis of SARS-CoV-2 by RT-qPCR in raw wastewater samples collected from three major wastewater treatment plants (WWTP) of the Paris area, serving more than 100,000 inhabitants. The study was conducted from 30 March to 23 April 2020, in the lockdown period in France which began on 17 March 2020. Samples were kept at 4°C and processed less than 24 hours after sampling.

Concentration and testing methods are described in detail (data not extracted here) and the authors estimated the total amount of viral RNA shed in stools in a given population based on the characteristics of the epidemic and what was known of the viral load from swabs taken from Covid-19 patients.

Study reliability

The study results fit well with those of other studies. No indication of the viability of viral RNA is reported.

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes No Yes Yes Yes

What else should I consider?

This is an observational correlational study. The results need replicating with similar sampling and testing procedure.

About the authors

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings

Tom Jefferson

Tom Jefferson, epidemiologist.