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Review 1: "Methodological Approach for Wastewater Based Epidemiological Studies for SARS-CoV-2"

Published onApr 14, 2022
Review 1: "Methodological Approach for Wastewater Based Epidemiological Studies for SARS-CoV-2"

RR:C19 Evidence Scale rating by reviewer:

  • Potentially informative. The main claims made are not strongly justified by the methods and data, but may yield some insight. The results and conclusions of the study may resemble those from the hypothetical ideal study, but there is substantial room for doubt. Decision-makers should consider this evidence only with a thorough understanding of its weaknesses, alongside other evidence and theory. Decision-makers should not consider this actionable, unless the weaknesses are clearly understood and there is other theory and evidence to further support it.



The manuscript attempts to establish a methodological approach for conducting WBE studies for SARS-CoV-2. The topic is interesting and there is a need for the identification of effective sampling techniques, the need for the adoption of effective virus concentration methods, and a need for robust and sensitive RT-qPCR assays in such complex matrices. The research was expected to provide recommendations on the most suitable sampling protocols for the determination of the number of infected individuals within a community, based on the outcomes of the research. The following are my comments in that regard:

  1. The research results need to be linked to the authors’ aims: the research reports the results of hourly sampling and the dynamics of RNA load on daily basis in sections 3.1 and 3.2, respectively. The research reports that higher RNA copies were observed at 6 am and 9 am and stabilized between 10 am and 1 am. However, the objective of the research was to define a methodological approach for conducting WBE studies in the framework of sampling protocols among many other things. In that regard, there is no reference as to how these results in sections 3.1 and 3.2 were used to recommend sampling protocols, which is an aim of the study. What are the implications of hourly sampling from a practical perspective? The same applies to composite sampling discussed in section 3.3.

  1. Estimation of community infection: community spread of the virus was estimated using average RNA copies of hourly, daily, and composite samples as described in section 3.4. The estimated number of infected individuals was highly varied between 28,200 and 281,700 based on the sampling window, which indicates high uncertainty in WBE. Also, there are no recommendations to aid researchers in selecting the best sampling timing or method based on the results presented here.

  1. Planning for WBE: on the 2nd paragraph of p. 17, the study only highlights general information that should be considered for planning WBE. However, there are no specific recommendations in that regard at all. How should samples be representative as suggested in point a? What is this defined sampling frequency mentioned in point c? How should grab and composite samples be selected? Some information is presented at the top of p. 18 but this needs to be linked with results from previous research, which would add strength to the manuscript.

  1. Conclusion: the conclusion in its current form is more of a literature review. Advised to rewrite to provide the researchers conclusion on the study.

  2. Abstract: similar to the conclusion section, the Abstract should be rewritten. 6. Methodology: the methodology section is too general specially in p.

  3. (2.2.1 Types of samples). There needs to be citation for specific methods such as p.8 under section 2.3.

Other comments:

  1. The manuscript requires comprehensive language editing as there are numerous grammatical and incorrect language expressions.

  2. There are many areas in the manuscript that are not supported by evidence in the literature such as paragraph 1 of p. 4. A complete review is required.

  3. Some expressions are not clear and ambiguous, such as: "inability to pinpoint specific locations" p.4 (line 6), "1.8 lakhs" p.5 (line 1).

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