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. 2022 Nov:28:102667.
doi: 10.1016/j.eti.2022.102667. Epub 2022 May 21.

The wave of the SARS-CoV-2 Omicron variant resulted in a rapid spike and decline as highlighted by municipal wastewater surveillance

Francesca Cutrupi  1 , Maria Cadonna  2 , Serena Manara  3 , Mattia Postinghel  2 , Giuseppina La Rosa  4 , Elisabetta Suffredini  5 , Paola Foladori  1
Affiliations

The wave of the SARS-CoV-2 Omicron variant resulted in a rapid spike and decline as highlighted by municipal wastewater surveillance

Francesca Cutrupi et al. Environ Technol Innov. 2022 Nov.

Abstract

This paper highlights the extraordinarily rapid spread of SARS-CoV-2 loads in wastewater that during the Omicron wave in December 2021-February 2022, compared with the profiles acquired in 2020-21 with 410 samples from two wastewater treatment plants (Trento+suburbs, 132,500 inhabitants). Monitoring of SARS-CoV-2 in wastewater focused on: (i) 3 samplings/week and analysis, (ii) normalization to calculate genomic units (GU) inh-1 d-1; (iii) calculation of a 7-day moving average to smooth daily fluctuations; (iv) comparison with the 'current active cases'/100,000 inh progressively affected by the mass vaccination. The time profiles of SARS-CoV-2 in wastewater matched the waves of active cases. In February-April 2021, a viral load of 1.0E＋07 GU inh-1 d - 1 corresponded to 700 active cases/100,000 inh. In July-September 2021, although the low current active cases, sewage revealed an appreciable SARS-CoV-2 circulation (in this period 2.2E＋07 GU inh-1 d-1 corresponded to 90 active cases/100,000 inh). Omicron was not detected in wastewater until mid-December 2021. The Omicron spread caused a 5-6 fold increase of the viral load in two weeks, reaching the highest peak (2.0-2.2E＋08 GU inh-1 d-1 and 4500 active cases/100,000 inh) during the pandemic. In this period, wastewater surveillance anticipated epidemiological data by about 6 days. In winter 2021-22, despite the 4-7 times higher viral loads in wastewater, hospitalizations were 4 times lower than in winter 2020-21 due to the vaccination coverage >80%. The Omicron wave demonstrated that SARS-CoV-2 monitoring of wastewater anticipated epidemiological data, confirming its importance in long-term surveillance.

Keywords: COVID-19; Omicron variant; SARS-CoV-2; Sewerage; Viral concentration; Wastewater-based epidemiology.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

None
Graphical abstract
Fig. 1
Fig. 1
Time-profiles of normalized SARS-CoV-2 RNA loads in wastewater. Open symbols are daily values, lines are the 7-day moving averages.
Fig. 2
Fig. 2
Comparison between 7-day moving averages of SARS-CoV-2 RNA loads in wastewater and current active cases.
Fig. 3
Fig. 3
Profiles during the Omicron wave in December 2021–February 2022. 7-day moving averages of SARS-CoV-2 RNA loads in wastewater compared to the current active cases. The presence (+) or absence (−) of Omicron variant found by two real-time PCR assays (JRC and ISS) are indicated.
Fig. 4
Fig. 4
Comparison of two successive winters (December–February 2020–21 and 2021–22). 7-day moving averages of SARS-CoV-2 RNA loads in wastewater, current active cases and hospitalizations are compared.
See this image and copyright information in PMC

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