Peer Review History

Original SubmissionJanuary 13, 2021
Decision Letter - Martin Chtolongo Simuunza, Editor

PONE-D-21-01351

Simulated sunlight decreases the viability of SARS-CoV-2 in mucus

PLOS ONE

Dear Dr. Sloan,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please attend to all the comments and concerns that have been raised by the reviewers. Ensure that you have given adequate background (introduction) to your work and that the results have been adequately discussed. You also need to improve the quality of your figures.

Please submit your revised manuscript by May 10 2021 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols

We look forward to receiving your revised manuscript.

Kind regards,

Martin Chtolongo Simuunza, PhD

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The COVID-19 outbreak is an ongoing global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, SARS-CoV-2 is less deadly but far more transmissible than other coronaviruses, such as MERS-CoV or SARS-CoV. The SARS-CoV-2 viruses remain viable and stable on various environmental conditions or surfaces for an extended period. In the current study, the authors aimed to assess the impact of stimulated sunlight on the viability of SARS-CoV-2. The study could provide useful information for pandemic mitigation efforts.

Major Issues:

1. It is unclear why sunlight would be considered a natural sterilizing medium. The study hypothesis and study plan need to be emphasized to highlight the importance of the current study. A more detailed background literature research should be reported as to how the current study can improve our understanding of SARS-CoV-2 from the already reported studies.

2. Sunlight or the sun’s angle is affected by geographical variations, weather condition and season. As reported previously by Ratnesar-Shumate et al. (2020), three different integrated UVB irradiance levels represented the spectra utilized span UVB irradiances throughout the different season. Could the authors explain why the solar output for spring and fall was selected for the current study?

3. For any reported results in the text, authors should refer the results to the exact figure. For example, “Fig 1 demonstrates that the viability of SARS-CoV-2 decreased significantly faster when exposed to sunlight versus exposure to the same conditions with sunlight removed (p ≤ 0.0045). Viral titer decreased most rapidly when the virus was suspended in the culture medium, from 3.12 to 1.5 log10 TCID50/mL in 37 minutes at 22.5°C and 34% RH.” It is unclear which graphs are this reported information belongs. There are six graphs in figure 1, and perhaps a more detailed explanation for each graph or condition would be beneficial for readers. Authors could consider reporting a summarized version of the supplementary data if they reported it multiple times in the text.

4. The discussion was vaguely written; the authors need to provide a direct comparison with other previous studies. It is also unclear what other additional information that the current study has provided to the field. A paragraph of limitation should be provided to the current study.

Minor Issues:

1. The figure quality needs to be improved significantly for publishable quality. Information on the figures appeared very blurry, and it was not easy to follow or read.

2. Abbreviation such as RH needs to be clearly stated in the text.

Reviewer #2: The manuscript by Sloan et al describes the evaluation of SARS-CoV-2 inactivation by artificial sunlight in the context of cell culture medium or a standardized mucous matrix. These studies showed that the sunlight system used in these studies effectively inactivated SARS-CoV-2 in the test system and also showed that the mucous matrix reduced the efficiency of inactivation.

Minor comment:

Line 16: Log10 (subscript)

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6. 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: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment 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. Registration is free. 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 PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Revision 1

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

________________________________________

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

________________________________________

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

________________________________________

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

________________________________________

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The COVID-19 outbreak is an ongoing global pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, SARS-CoV-2 is less deadly but far more transmissible than other coronaviruses, such as MERS-CoV or SARS-CoV. The SARS-CoV-2 viruses remain viable and stable on various environmental conditions or surfaces for an extended period. In the current study, the authors aimed to assess the impact of stimulated sunlight on the viability of SARS-CoV-2. The study could provide useful information for pandemic mitigation efforts.

Major Issues:

1. It is unclear why sunlight would be considered a natural sterilizing medium. The study hypothesis and study plan need to be emphasized to highlight the importance of the current study. A more detailed background literature research should be reported as to how the current study can improve our understanding of SARS-CoV-2 from the already reported studies.

Response: A paragraph has been added to the Introduction explaining why the UV radiation present in sunlight can be used as a natural sterilizing mechanism to deactivate microorganisms, including SARS-CoV-2. We have also referenced other studies that have used UV radiation and sunlight to deactivate SARS-CoV-2 and described how the findings of our research will improve our understanding of the virus.

2. Sunlight or the sun’s angle is affected by geographical variations, weather condition and season. As reported previously by Ratnesar-Shumate et al. (2020), three different integrated UVB irradiance levels represented the spectra utilized span UVB irradiances throughout the different season. Could the authors explain why the solar output for spring and fall was selected for the current study?

Response: We chose to examine the ability of simulated sunlight to deactivate SARS-CoV-2 using our solar simulator set to “1 sun”, which is defined as full sunlight intensity on a bright clear day on Earth and measuring approximately 1000 W/m2 [Tables for Reference Solar Spectral Irradiances: Direct Normal and Hemispherical on 37 Tilted Surface". 2008. doi:10.1520/G0173-03R08]. At this setting, the UVB emitted by our particular solar simulator produced a UVB irradiance of 1.28 W/m2 at 1 sun, which happened to be equivalent to the amount of UVB emitted during the day on both the spring solstice and autumn equinox. As this level of UVB represented the irradiance emitted on separate days during two distinct seasons, 1 sun was considered an ideal level of solar output to examine. We also felt that less intense solar outputs (i.e. less than what would normally be observed during summer) resulting in prolonged viral sustainability would have more real-world implications.

3. For any reported results in the text, authors should refer the results to the exact figure. For example, “Fig 1 demonstrates that the viability of SARS-CoV-2 decreased significantly faster when exposed to sunlight versus exposure to the same conditions with sunlight removed (p ≤ 0.0045). Viral titer decreased most rapidly when the virus was suspended in the culture medium, from 3.12 to 1.5 log10 TCID50/mL in 37 minutes at 22.5°C and 34% RH.” It is unclear which graphs are this reported information belongs. There are six graphs in figure 1, and perhaps a more detailed explanation for each graph or condition would be beneficial for readers. Authors could consider reporting a summarized version of the supplementary data if they reported it multiple times in the text.

Response: Each graph in Figure 1 has been described and referenced more clearly. Supplementary Table 2 has become Table 1, as it was referenced several times in the Results section.

4. The discussion was vaguely written; the authors need to provide a direct comparison with other previous studies. It is also unclear what other additional information that the current study has provided to the field. A paragraph of limitation should be provided to the current study.

Response: The Discussion has been rewritten to include a more direct comparison with the only other study reported to date examining simulated sunlight on the decay rate of SARS-CoV-2 on surfaces (i.e. Ratnesar-Shumate et al. 2020). A supplementary figure has also been included to directly compare the two studies’ results. Lastly, a paragraph discussing limitations has been added.

Minor Issues:

1. The figure quality needs to be improved significantly for publishable quality. Information on the figures appeared very blurry, and it was not easy to follow or read.

Response: We have submitted our original figure to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool at https://pacev2.apexcovantage.com/increased. To the best of our knowledge, the submitted figure should now conform to PLOS ONE standards. Unfortunately, while the PACE-created Fig 1 is extremely clear in its submitted .tif file format, it appears blurry in the final PDF submission. It is our hope that we can work together with the journal editors if the quality of Fig 1 continues to be a problem.

2. Abbreviation such as RH needs to be clearly stated in the text.

Response: The “RH” abbreviation has been defined as “relative humidity” in the Materials and Methods section. We have also defined the abbreviation “W/m2” as “watts per square meter” and have spelled out “MRads” as “megarads”.

Reviewer #2: The manuscript by Sloan et al describes the evaluation of SARS-CoV-2 inactivation by artificial sunlight in the context of cell culture medium or a standardized mucous matrix. These studies showed that the sunlight system used in these studies effectively inactivated SARS-CoV-2 in the test system and also showed that the mucous matrix reduced the efficiency of inactivation.

Minor comment:

Line 16: Log10 (subscript)

Response: The subscript has been included.

________________________________________

6. 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: No

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment 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. Registration is free. 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 PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Attachments
Attachment
Submitted filename: Respone to Reviewers.docx
Decision Letter - Martin Chtolongo Simuunza, Editor

Simulated sunlight decreases the viability of SARS-CoV-2 in mucus

PONE-D-21-01351R1

Dear Dr. Sloan,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Martin Chtolongo Simuunza, PhD

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: The only concern is the result section which appeared to be relatively short and might need to be elaborate further.

Reviewer #2: No additional comments

Extra characters to meet the 100 character minimum...……………………………………………………...

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7. 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: No

Formally Accepted
Acceptance Letter - Martin Chtolongo Simuunza, Editor

PONE-D-21-01351R1

Simulated sunlight decreases the viability of SARS-CoV-2 in mucus

Dear Dr. Sloan:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Martin Chtolongo Simuunza

Academic Editor

PLOS ONE

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