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. 2021 May 17:12:664477.
doi: 10.3389/fmicb.2021.664477. eCollection 2021.

Viral RNA in City Wastewater as a Key Indicator of COVID-19 Recrudescence and Containment Measures Effectiveness

Nathalie Wurtz  1   2 , Alexandre Lacoste  3 , Priscilla Jardot  1 , Alain Delache  4 , Xavier Fontaine  3 , Maxime Verlande  3 , Alexandre Annessi  3 , Audrey Giraud-Gatineau  1   2 , Hervé Chaudet  2   5 , Pierre-Edouard Fournier  2   5 , Patrick Augier  3 , Bernard La Scola  1   2
Affiliations

Viral RNA in City Wastewater as a Key Indicator of COVID-19 Recrudescence and Containment Measures Effectiveness

Nathalie Wurtz et al. Front Microbiol. .

Abstract

In recent years, and more specifically at the beginning of the COVID-19 crisis, wastewater surveillance has been proposed as a tool to monitor the epidemiology of human viral infections. In the present work, from July to December 2020, the number of copies of SARS-CoV-2 RNA in Marseille's wastewater was correlated with the number of new positive cases diagnosed in our Institute of Infectious Disease, which tested about 20% of the city's population. Number of positive cases and number of copies of SARS-CoV-2 RNA in wastewater were significantly correlated (p = 0.013). During the great epidemic peak, from October to December 2020, the curves of virus in the sewers and the curves of positive diagnoses were perfectly superposed. During the summer period, the superposition of curves was less evident as subject to many confounding factors that were discussed. We also tried to correlate the effect of viral circulation in wastewater with containment measures, probably the most unbiased correlation on their potential inflection effect of epidemic curves. Not only is this correlation not obvious, but it also clearly appears that the drop in cases as well as the drop in the viral load in the sewers occur before the containment measures. In fact, this suggests that there are factors that initiate the end of the epidemic peak independently of the containment measure. These factors will therefore need to be explored more deeply in the future.

Keywords: COVID-19; RNA; SARS-CoV-2; sewers; wastewater.

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Conflict of interest statement

AD was employed by the company CAMGAU Consulting. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Wastewater networks in Marseille. The separate network (red lines) drains the major surface part of Marseille wastewater. The combined network (green lines), that contains a mixture of rainwater and wastewater, drains the city center. The blue circle represents the sampling point.
FIGURE 2
FIGURE 2
Variations in mean outdoor temperature (dark gray) and rain fall (light gray) during the period of study (from July 1 to December 15). Copy number of SARS-CoV-2 in RU (green) and RS (red) wastewater networks were represented.
FIGURE 3
FIGURE 3
Correlation of SARS-CoV-2 Marseille new positives cases (blue curve) and copy number of SARS-CoV-2 in RU + RS wastewater networks (orange curve). Eight-days moving average was represented. The measures implemented by government were positioned at the day of application. In gray, the period where efficiency of the measures can be observed.
See this image and copyright information in PMC

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