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Review 2: "Wastewater Surveillance of SARS-CoV-2 across 40 U.S. states"

This preprint reports a high detection rate of SARS-CoV-2 using wastewater surveillance and finds that virus detection precedes clinical indicators. Reviewers deem these findings potentially informative, recommending large scale studies to confirm findings.

Published onJun 16, 2021
Review 2: "Wastewater Surveillance of SARS-CoV-2 across 40 U.S. states"
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key-enterThis Pub is a Review of
Wastewater Surveillance of SARS-CoV-2 across 40 U.S. states

AbstractWastewater-based disease surveillance is a promising approach for monitoring community outbreaks. Here we describe a nationwide campaign to monitor SARS-CoV-2 in the wastewater of 159 counties in 40 U.S. states, covering 13% of the U.S. population from February 18 to June 2, 2020. Out of 1,751 total samples analyzed, 846 samples were positive for SARS-CoV-2 RNA, with overall viral concentrations declining from April to May. Wastewater viral titers were consistent with, and appeared to precede, clinical COVID-19 surveillance indicators, including daily new cases. Wastewater surveillance had a high detection rate (>80%) of SARS-CoV-2 when the daily incidence exceeded 13 per 100,000 people. Detection rates were positively associated with wastewater treatment plant catchment size. To our knowledge, this work represents the largest-scale wastewater-based SARS-CoV-2 monitoring campaign to date, encompassing a wide diversity of wastewater treatment facilities and geographic locations. Our findings demonstrate that a national wastewater-based approach to disease surveillance may be feasible and effective.

RR:C19 Evidence Scale rating by reviewer:

  • Reliable. The main study claims are generally justified by its methods and data. The results and conclusions are likely to be similar to the hypothetical ideal study. There are some minor caveats or limitations, but they would/do not change the major claims of the study. The study provides sufficient strength of evidence on its own that its main claims should be considered actionable, with some room for future revision.



The paper reports results from wastewater SARS-CoV-2 measurements that took place in the USA between March and May of 2020. While these types of studies are common and increasingly being reported by different research groups and jurisdictions, what sets this study apart is the number of samples that were analyzed and the geography and population covered by the sampling. The group reporting the work are also amongst the first to carry out this type of sampling and analysis.

The limitations of the study, which were also acknowledged by the authors, are the low number of samples analyzed in March compared to April and May and the fact that the different jurisdictions mailed samples to the authors’ laboratory. The different sampling methods carried out by the different groups could affect the results, as indicated by the authors as well.

The methods used to quantify SARS-CoV-2 levels are appropriate and the manner in which the analysis was carried out on the generated data can be used to justify the conclusions made by the study. What would strengthen the work would be data that covers the USA over the past year as opposed to only 3 months early in the pandemic. If similar trends and predictability with regards to wastewater values preceding or mirroring hospital admissions and SARS-CoV-2 infection incidence rates, then stronger support for the conclusions of the paper would be possible.


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