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. 2020 Nov 20:744:140911.
doi: 10.1016/j.scitotenv.2020.140911. Epub 2020 Jul 14.

Presence and infectivity of SARS-CoV-2 virus in wastewaters and rivers

Sara Giordana Rimoldi  1 , Fabrizio Stefani  2 , Anna Gigantiello  1 , Stefano Polesello  3 , Francesco Comandatore  4 , Davide Mileto  1 , Mafalda Maresca  1 , Concetta Longobardi  1 , Alessandro Mancon  1 , Francesca Romeri  1 , Cristina Pagani  1 , Francesca Cappelli  5 , Claudio Roscioli  3 , Lorenzo Moja  6 , Maria Rita Gismondo  1 , Franco Salerno  3
Affiliations

Presence and infectivity of SARS-CoV-2 virus in wastewaters and rivers

Sara Giordana Rimoldi et al. Sci Total Environ. .

Abstract

The presence of SARS-CoV-2 in raw wastewaters has been demonstrated in many countries affected by this pandemic. Nevertheless, virus presence and infectivity in treated wastewaters, but also in the receiving water bodies are still poorly investigated. In this study, raw and treated samples from three wastewater treatment plants, and three river samples within the Milano Metropolitan Area, Italy, were surveyed for SARS-CoV-2 RNA detection by means of real time RT-PCR and infectivity test on culture cells. SARS-CoV-2 RNA was detected in raw, but not in treated wastewaters (four and two samples, respectively, sampled in two dates). The isolated virus genome was sequenced, and belonged to the strain most spread in Europe and similar to another found in the same region. RNA presence in raw wastewater samples decreased after eight days, probably following the epidemiological trend estimated for the area. Virus infectivity was always null, indicating the natural decay of viral pathogenicity in time from emission. Samples from receiving rivers (three sites, sampled in the same dates as wastewaters) showed in some cases a positivity to real time RT-PCR, probably due to non-treated, or inefficiently treated discharges, or to the combined sewage overflows. Nevertheless, also for rivers infectivity was null. Risks for public health should be limited, although a precautionary approach to risk assessment is here advocated, giving the preliminary nature of the presented data.

Keywords: Genome; Infectivity; Milano; SARS-CoV-2; Wastewater.

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Conflict of interest statement

Declaration of competing interest 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

Unlabelled Image
Graphical abstract
Fig. 1
Fig. 1
Map of Milano Metropolitan Area, with the two main river basins highlighted: 1) the Lambro Meridionale (LM) River, closed and sampled on Mirasole bridge; 2) the Lambro (L) River, closed and sampled on Melegnano bridge. The Vettabbia Canal is also indicated. Approximate locations of all WWTPs are indicated with squares whose size is proportional to their capacity (population equivalent). WWTP-A, the main plant of Monza and Brianza, WWTP-B and WWTP-C, the main plants of Milano, have been investigated in this study.
Fig. 2
Fig. 2
Trend of COVID-19 cases diagnosed in Province of Milano and Monza and Brianza (source: Protezione Civile, https://github.com/pcm-dpc/COVID-19/blob/master/dati-province/dpc-covid19-ita-province.csv). On the left y-axis, relative cases represent the new daily cases divided by the resident population in each Province. On the right y-axis, absolute cases represent the weekly window mean of the sum of the new daily absolute cases of both Provinces.
Fig. 3
Fig. 3
Maximum Likelihood phylogenetic tree including the the Hsacco-1 strain sequenced in this work and the 300 most similar SARS-CoV-2 strains retrieved from GISAID database. Geographic strains metadata, as retrieved from GISAID database, were mapped on the tree: the isolation continent is reported on the inner circle and, for the Italian strains only, the isolation city is reported on the external circle. The labels of the strains isolated in Milan are reported with larger size and the strain sequenced in this work is coloured in red. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
See this image and copyright information in PMC

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