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. 2022 Dec 9;19(24):16588.
doi: 10.3390/ijerph192416588.

Calibration of Methods for SARS-CoV-2 Environmental Surveillance: A Case Study from Northwest Tuscany

Marco Verani  1 , Ileana Federigi  1 , Sara Muzio  1 , Giulia Lauretani  1 , Piergiuseppe Calà  2 , Fabrizio Mancuso  3 , Roberto Salvadori  4 , Claudia Valentini  5 , Giuseppina La Rosa  6 , Elisabetta Suffredini  7 , Annalaura Carducci  1
Affiliations

Calibration of Methods for SARS-CoV-2 Environmental Surveillance: A Case Study from Northwest Tuscany

Marco Verani et al. Int J Environ Res Public Health. .

Abstract

The current pandemic has provided an opportunity to test wastewater-based epidemiology (WBE) as a complementary method to SARS-CoV-2 monitoring in the community. However, WBE infection estimates can be affected by uncertainty factors, such as heterogeneity in analytical procedure, wastewater volume, and population size. In this paper, raw sewage SARS-CoV-2 samples were collected from four wastewater treatment plants (WWTPs) in Tuscany (Northwest Italy) between February and December 2021. During the surveillance period, viral concentration was based on polyethylene glycol (PEG), but its precipitation method was modified from biphasic separation to centrifugation. Therefore, in parallel, the recovery efficiency of each method was evaluated at lab-scale, using two spiking viruses (human coronavirus 229E and mengovirus vMC0). SARS-CoV-2 genome was found in 80 (46.5%) of the 172 examined samples. Lab-scale experiments revealed that PEG precipitation using centrifugation had the best recovery efficiency (up to 30%). Viral SARS-CoV-2 load obtained from sewage data, adjusted by analytical method and normalized by population of each WWTP, showed a good association with the clinical data in the study area. This study highlights that environmental surveillance data need to be carefully analyzed before their use in the WBE, also considering the sensibility of the analytical methods.

Keywords: HCoV-229E; SARS-CoV-2; mengovirus VMC0; wastewater surveillance; wastewater-based epidemiology.

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Conflict of interest statement

The authors declare no conflicts of interest. The companies had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Location of the WWTPs in the study area (GEOscopio WMS, Tuscany Regional Government, https://www.regione.toscana.it/-/geoscopio (accessed on 31 October 2022)).
Figure 2
Figure 2
Flowchart of the analytical procedures.
Figure 3
Figure 3
Results of the environmental monitoring of SARS-CoV-2 in sewage (GC/L). During the first monitoring period, the number of samples was less than the second part. LOD = limit of detection; min = minimum; max = maximum; GM = geometric mean.
Figure 4
Figure 4
Relationship between vMC0 concentration detected with the two different methods. Magenta dots are experimental results and blue line is the linear model for such data (the light blue lines represent the 95% confidence interval).
Figure 5
Figure 5
SARS-CoV-2 normalized monitoring data (blue histogram). Concentration obtained with method A has been adjusted on the basis of method B (green histogram). Dash red line represents the COVID-19 clinical cases, highlighting the spread of three variants of concern (VoC): Alpha (B.1.117), Delta (B.1.617.2), Omicron (B.1.1.529) [24].
See this image and copyright information in PMC

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