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. 2021 Jul 15;202:117433. doi: 10.1016/j.watres.2021.117433

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© 2021 The Authors. Published by Elsevier Ltd.

Since January 2020 Elsevier has created a COVID-19 resource centre with free information in English and Mandarin on the novel coronavirus COVID-19. The COVID-19 resource centre is hosted on Elsevier Connect, the company's public news and information website. Elsevier hereby grants permission to make all its COVID-19-related research that is available on the COVID-19 resource centre - including this research content - immediately available in PubMed Central and other publicly funded repositories, such as the WHO COVID database with rights for unrestricted research re-use and analyses in any form or by any means with acknowledgement of the original source. These permissions are granted for free by Elsevier for as long as the COVID-19 resource centre remains active.

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Fig. 1 — Correlations between measured wastewater SARS-CoV-2 concentrations and reported COVID-19 case counts (y-axis) vary depending on lead time (x-axis), correlation metric (panel a), incidence metric (b), and time (c) in Boston, Massachusetts during April 2020 to March 2021. Wastewater data were collected using methods previously described (Wu et al. 2020a; Wu et al. 2020b; data available at https://www.mwra.com/biobot/biobotdata.htm, North system). Case data includes cases in Suffolk and Middlesex Counties, MA, which are served by the wastewater plant (USA Facts; data available at https://usafacts.org/visualizations/coronavirus-covid-19-spread-map). Zero lead time refers to the correlation between wastewater and the case counts on the day of the wastewater sampling. Positive lead times refer to wastewater correlated with later case counts (e.g., a lead time of +3 days refers to the correlation between wastewater and cases 3 days later). Negative lead times refer to wastewater correlated with earlier case counts. Colors are only used to distinguish curves; the same color in different subplots are not necessarily related. (a) Spearman: Spearman correlation between 7-day average case counts (i.e., mean number of new case counts over the day of wastewater sampling and the previous 6 days) and wastewater virus concentrations. This is the baseline analysis. (a) Pearson: Pearson correlation between 7-day average case counts and wastewater virus concentrations. (a) Pearson (log): Pearson correlation between 7-day average case counts and base-10 logarithms of wastewater virus concentrations. (b) 7-day average (lagging): Baseline analysis; same as (a) Spearman. (b) 7-day average (center): Spearman correlation between centered 7-day average case counts (i.e., mean number of new case counts over the day of wastewater sampling, the preceding 3 days, and the following 3 days) and wastewater virus concentrations. (b) Raw case counts: Spearman correlation between daily number of new case counts (without smoothing) and wastewater virus concentrations. (c) Baseline analysis like in (a) Spearman, but using data only from each calendar quarter (e.g., 2020 Q2 is April-June 2020).