Dear Mrs. Bourner,

Thank you very much for submitting your manuscript "Clinical characterization of Lassa fever: a systematic review of clinical reports and research to inform clinical trial design" for consideration at PLOS Neglected Tropical Diseases. As with all papers reviewed by the journal, your manuscript was reviewed by members of the editorial board and by several independent reviewers. In light of the reviews (below this email), we would like to invite the resubmission of a significantly-revised version that takes into account the reviewers' comments.

We cannot make any decision about publication until we have seen the revised manuscript and your response to the reviewers' comments. Your revised manuscript is also likely to be sent to reviewers for further evaluation.

When you are ready to resubmit, please upload the following:

[1] A letter containing a detailed list of your responses to the review comments and a description of the changes you have made in the manuscript. Please note while forming your response, if your article is accepted, you may have the opportunity to make the peer review history publicly available. The record will include editor decision letters (with reviews) and your responses to reviewer comments. If eligible, we will contact you to opt in or out.

[2] Two versions of the revised manuscript: one with either highlights or tracked changes denoting where the text has been changed; the other a clean version (uploaded as the manuscript file).

Important additional instructions are given below your reviewer comments.

Please prepare and submit your revised manuscript within 60 days. If you anticipate any delay, please let us know the expected resubmission date by replying to this email. Please note that revised manuscripts received after the 60-day due date may require evaluation and peer review similar to newly submitted manuscripts.

Thank you again for your submission. We hope that our editorial process has been constructive so far, and we welcome your feedback at any time. Please don't hesitate to contact us if you have any questions or comments.

Sincerely,

Manuel Schibler

Associate Editor

PLOS Neglected Tropical Diseases

Andrés Henao-Martínez

Deputy Editor

PLOS Neglected Tropical Diseases

***********************

Reviewer's Responses to Questions

Key Review Criteria Required for Acceptance?

As you describe the new analyses required for acceptance, please consider the following:

Methods

-Are the objectives of the study clearly articulated with a clear testable hypothesis stated?

-Is the study design appropriate to address the stated objectives?

-Is the population clearly described and appropriate for the hypothesis being tested?

-Is the sample size sufficient to ensure adequate power to address the hypothesis being tested?

-Were correct statistical analysis used to support conclusions?

-Are there concerns about ethical or regulatory requirements being met?

Reviewer #1: The objectives of this study was to analyze publication on LF treatment in the effort of finding better standards for LF studies concerning the inclusion/exclusion and outcome criteria as well as the clinical case definition. The study design was very robust concerning the search criteria as well as the analysis of the data. The number of included studies in this analysis is very comprehensive. The statistics are exclusively descriptive, as this study does not formulate a clasical hypothesis. There are no ethical concerns.

Reviewer #2: The study is a systematic review of the literature reporting the clinical signs and symptoms of Lassa fever. The suggested major revisions prior to acceptance are listed below.

1. The link between this review manuscript and how its data might be used to guide clinical trials needs to be better established. In the Introduction section, consider describing how other review papers guided clinical trials for treatments for other febrile illnesses.

2. In the Discussion section consider adding a subsection describing how the results might be used to guide future ribavirin trials. Is there a proposed set of symptoms that should be considered for a suspected case definition?

3. While the focus of the study is to provide information regarding ribavirin trials, there is little information in the manuscript about selected studies that included ribavirin components. How many of the studies included ribavirin? Was ribavirin generally found to be effective in those studies?

4. The premise of this article seems to be that Lassa symptoms can be standardized across geographic regions. What are the implications of standardization? Different countries have different strains of LF. Also, public health units differ by time to clinical presentation and laboratory capacity (for evaluating lab-based items contributing to a suspected case definition). While it may be beyond the scope of this study to report in detail on those challenges, they do seem worth mentioning. Consider adding a subsection in the Discussion section about the challenges of standardization.

5. Consider adding a subsection in the Discussion sections about the study limitations; e.g., test validity, little distinction between acute and long-term exposure. For instance, IgG testing measures long-term exposure and is associated with different symptoms than Ag+ acute cases.

Reviewer #3: (No Response)

--------------------

Results

-Does the analysis presented match the analysis plan?

-Are the results clearly and completely presented?

-Are the figures (Tables, Images) of sufficient quality for clarity?

Reviewer #1: The analysis follows a clear plan, the presentation of the result is clear and comprehensive. All figures and tables are of good quality. It is of note that the results include a broad range of clinical symptoms that go beyond what is often included in clincal case definitions. This corresponds to the numerous case reports that represent the broad clinical picture of LF and is thus an important contribution. The authors also recorded which clinical symptoms were more frequent after baseline.

The authors alos analyzed the frequency of bleeding at different sites and found haematuria the most frequent presentation. However, it should be more thoroughly explained which kinds of haemturia were documented, and if cases of microhaematuria were included, as it can be a resut of kidney injury but does not necessarily represent true bleeding in the stricter sense to my opinion.

Overall, the results are very informative in the effort of finding better standards for clinical studies on LF

Reviewer #2: The analysis does match the analysis plan, the results are clearly and completely presented, and the figures are of sufficient quality for clarity.

Reviewer #3: (No Response)

--------------------

Conclusions

-Are the conclusions supported by the data presented?

-Are the limitations of analysis clearly described?

-Do the authors discuss how these data can be helpful to advance our understanding of the topic under study?

-Is public health relevance addressed?

Reviewer #1: The conclusion are sound in nature but it should be pointed out a little more that this analysis is strictly descariptive and that in order to reach the declared goal of establishing standardized protocols, results would need to be graded (for discussion). the rest of the discussion of the result is very well suited to inform the understanding of the topic.

Reviewer #2: The link between this review manuscript and how its data might be used to guide clinical trials needs to be better established. In the Introduction section, consider describing how other review papers guided clinical trials for treatments for other febrile illnesses.

Reviewer #3: (No Response)

--------------------

Editorial and Data Presentation Modifications?

Use this section for editorial suggestions as well as relatively minor modifications of existing data that would enhance clarity. If the only modifications needed are minor and/or editorial, you may wish to recommend “Minor Revision” or “Accept”.

Reviewer #1: Figure 3 needs to be graphically edited as the numbers are very hard to read, even on a large screen

Other than this minior issue I would recommend to accept

Reviewer #2: Minor suggested revisions:

1. Lines 12-13: "all studies were included"

This statement is overly broad as the literature search did not cover all available bibliographic databases and search engines (e.g., Google Scholar)

2. Line 17: what arose from these discussions?

3. Lines 54-56. Further evidence in the form of clinical trials is required both to confirm the efficacy and safety of ribavirin and to test new therapies.

While this statement is true, consider elaborating on this statement by mentioning the advantages of testing in additional geographic regions, larger sample sizes, accounting for different LF strains, etc.

4. Line 59-60: the clinical characteristics of LF and patient outcomes

The second component of the sentence clinical characteristics of patient outcomes is confusing. Consider rewording.

5. Line 87: spell out acronym for REDCap on first occurrence

6. Lines 102-113: Overuse of “We”

7. Line 225 (Table 5). The definition of laboratory confirmation is extremely influential, particularly at baseline. For instance, Ag ELISA measures acute exposure, IgM measures recent exposure, and IgG measures long-term exposure. It may be helpful to review Table 5 by diagnostic approach to determine whether pooling is justified.

8. Line 262 – “An agreed”

Consider replacing agreed with uniform.

9. Lines 284-287: What are the reasons for this? Limited laboratory capacity?

10. Discussion section: seems to be missing any mention of the need for improved diagnostics and rapid testing

Reviewer #3: (No Response)

--------------------

Summary and General Comments

Use this section to provide overall comments, discuss strengths/weaknesses of the study, novelty, significance, general execution and scholarship. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. If requesting major revision, please articulate the new experiments that are needed.

Reviewer #1: this paper provides a meaningful contribution and is the largest analysis of the kind to my knowledge.

Reviewer #2: General comments

The study addresses a void in the literature by providing a comprehensive systematic review of the literature reporting the clinical signs and symptoms of Lassa fever to guide future ribavirin trials.

Major comments

1. The link between this review manuscript and how its data might be used to guide clinical trials needs to be better established. In the Introduction section, consider describing how other review papers guided clinical trials for treatments for other febrile illnesses.

2. In the Discussion section consider adding a subsection describing how the results might be used to guide future ribavirin trials. Is there a proposed set of symptoms that should be considered for a suspected case definition?

3. While the focus of the study is to provide information regarding ribavirin trials, there is little information in the manuscript about selected studies that included ribavirin components. How many of the studies included ribavirin? Was ribavirin generally found to be effective in those studies?

4. The premise of this article seems to be that Lassa symptoms can be standardized across geographic regions. What are the implications of standardization? Different countries have different strains of LF. Also, public health units differ by time to clinical presentation and laboratory capacity (for evaluating lab-based items contributing to a suspected case definition). While it may be beyond the scope of this study to report in detail on those challenges, they do seem worth mentioning. Consider adding a subsection in the Discussion section about the challenges of standardization.

5. Consider adding a subsection in the Discussion sections about the study limitations; e.g., test validity, little distinction between acute and long-term exposure. For instance, IgG testing measures long-term exposure and is associated with different symptoms than Ag+ acute cases.

Minor comments

1. Lines 12-13: "all studies were included"

This statement is overly broad as the literature search did not cover all available bibliographic databases and search engines (e.g., Google Scholar)

2. Line 17: what arose from these discussions?

3. Lines 54-56. Further evidence in the form of clinical trials is required both to confirm the efficacy and safety of ribavirin and to test new therapies.

While this statement is true, consider elaborating on this statement by mentioning the advantages of testing in additional geographic regions, larger sample sizes, accounting for different LF strains, etc.

4. Line 59-60: the clinical characteristics of LF and patient outcomes

The second component of the sentence clinical characteristics of patient outcomes is confusing. Consider rewording.

5. Line 87: spell out acronym for REDCap on first occurrence

6. Lines 102-113: Overuse of “We”

7. Line 225 (Table 5). The definition of laboratory confirmation is extremely influential, particularly at baseline. For instance, Ag ELISA measures acute exposure, IgM measures recent exposure, and IgG measures long-term exposure. It may be helpful to review Table 5 by diagnostic approach to determine whether pooling is justified.

8. Line 262 – “An agreed”

Consider replacing agreed with uniform.

9. Lines 284-287: What are the reasons for this? Limited laboratory capacity?

10. Discussion section: seems to be missing any mention of the need for improved diagnostics and rapid testing.

Reviewer #3: Merson et al., report valuable information about the signs, symptoms and outcomes of infection with Lassa virus. I believe that the following points are important and deserve further clarification.

More data regarding Lassa virus epidemiology in the 'Introduction' section may further enhance the structural feature of the manuscript. The article " Systematic review and meta-analysis of the epidemiology of Lassa virus in humans, rodents and other mammals in sub-Saharan Africa. PLoS Negl Trop Dis. 2020 Aug 26;14(8):e0008589" may be useful to provide such information to the readers.

Line 61: I would suggest that the authors reword the purpose of the study. “individual-level data” is confusing with the reviews performed on individual patient data from the original databases of the authors of the included studies. This concept of individual data from included study participants should also be clarified throughout the manuscript.

Line 99: The authors should clarify the detection methods and the targets (RNA, viral antigen, antibodies, IgM, IgG…) searched to be considered as confirmed cases of Lassa virus infection.

Line 102-106: In addition to the proportions reported, authors should ideally (if possible) provide the individual data of the included studies.

The signs and symptoms reported in this work should be fully discussed in relation to the multiple other febrile illnesses and haemorrhagic fevers due to other pathogens present in these endemic areas of West Africa and presenting the same clinical picture.

The discussion needs more references to better inform the concept of the research. For example, line 291, what is the work that argues that pregnant women are at higher risk of death from infection with Lassa virus.

The review authors should clearly describe the limitations of this article.

--------------------

PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: Yes: Jeffrey G. Shaffer

Reviewer #3: No

Figure Files:

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email us at figures@plos.org.

Data Requirements:

Please note that, as a condition of publication, PLOS' data policy requires that you make available all data used to draw the conclusions outlined in your manuscript. Data must be deposited in an appropriate repository, included within the body of the manuscript, or uploaded as supporting information. This includes all numerical values that were used to generate graphs, histograms etc.. For an example see here: http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001908#s5.

Reproducibility:

To enhance the reproducibility of your results, we recommend that you deposit your laboratory protocols in protocols.io, where a protocol can be assigned its own identifier (DOI) such that it can be cited independently in the future. Additionally, PLOS ONE offers an option to publish peer-reviewed clinical study protocols. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols

Dear Mrs. Bourner,

We are pleased to inform you that your manuscript 'Clinical characterization of Lassa fever: a systematic review of clinical reports and research to inform clinical trial design' has been provisionally accepted for publication in PLOS Neglected Tropical Diseases.

Before your manuscript can be formally accepted, we would like you to address two more minor concerns:

1. Page 5, line 54: please replace "although this figure is lower (12%) in more recent studies" by "although this figure is lower (12%) in a more recent study"

2. Page 9, lines 150-151: please correct the percentage of quasi-randomised studies; it's 1 (or 1.4), not 2%

You will also need to complete some formatting changes, which you will receive in a follow up email. A member of our team will be in touch with a set of requests.

Please note that your manuscript will not be scheduled for publication until you have made the required changes, so a swift response is appreciated.

IMPORTANT: The editorial review process is now complete. PLOS will only permit corrections to spelling, formatting or significant scientific errors from this point onwards. Requests for major changes, or any which affect the scientific understanding of your work, will cause delays to the publication date of your manuscript.

Should you, your institution's press office or the journal office choose to press release your paper, you will automatically be opted out of early publication. We ask that you notify us now if you or your institution is planning to press release the article. All press must be co-ordinated with PLOS.

Thank you again for supporting Open Access publishing; we are looking forward to publishing your work in PLOS Neglected Tropical Diseases.

Best regards,

Manuel Schibler

Associate Editor

PLOS Neglected Tropical Diseases

Andrés Henao-Martínez

Deputy Editor

PLOS Neglected Tropical Diseases

***********************************************************

Reviewer's Responses to Questions

Key Review Criteria Required for Acceptance?

As you describe the new analyses required for acceptance, please consider the following:

Methods

-Are the objectives of the study clearly articulated with a clear testable hypothesis stated?

-Is the study design appropriate to address the stated objectives?

-Is the population clearly described and appropriate for the hypothesis being tested?

-Is the sample size sufficient to ensure adequate power to address the hypothesis being tested?

-Were correct statistical analysis used to support conclusions?

-Are there concerns about ethical or regulatory requirements being met?

Reviewer #3: (No Response)

**********

Results

-Does the analysis presented match the analysis plan?

-Are the results clearly and completely presented?

-Are the figures (Tables, Images) of sufficient quality for clarity?

Reviewer #3: (No Response)

**********

Conclusions

-Are the conclusions supported by the data presented?

-Are the limitations of analysis clearly described?

-Do the authors discuss how these data can be helpful to advance our understanding of the topic under study?

-Is public health relevance addressed?

Reviewer #3: (No Response)

**********

Editorial and Data Presentation Modifications?

Use this section for editorial suggestions as well as relatively minor modifications of existing data that would enhance clarity. If the only modifications needed are minor and/or editorial, you may wish to recommend “Minor Revision” or “Accept”.

Reviewer #3: (No Response)

**********

Summary and General Comments

Use this section to provide overall comments, discuss strengths/weaknesses of the study, novelty, significance, general execution and scholarship. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. If requesting major revision, please articulate the new experiments that are needed.

Reviewer #3: Although the authors have adequately addressed my suggestions, I think that the citation of the 30% case fatality ratio from the meta-analysis [5] might not be attenuated by the citation [6] which is an original article and therefore difficult to compare. In addition, the authors of the present review report in the abstract the same 30% case fatality ratio found from their own work.

**********

PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #3: No