PONE-D-22-12653Evaluating Fomite Risk of Brown Paper Bags Storing Personal Protective Equipment Exposed to SARS-CoV-2: A Quasi-Experimental StudyPLOS ONE

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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: Yes

Reviewer #2: Yes

Reviewer #3: Yes

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

Reviewer #1: I Don't Know

Reviewer #2: Yes

Reviewer #3: N/A

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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: No

Reviewer #3: 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

Reviewer #3: 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: Overall Comments:

Thank you for the opportunity to review your work! Overall, I think this is a well written paper and an important investigation that has a clear benefit to informing protocols for used PPE storage. I have some major and minor comments to consider to add clarity and context in some places for readers.

Major Comments:

What was the swab efficiency? This will have important implications for interpreting % positive.

The objective of the Controls portion of the study is a little unclear. Is this related to contamination of bags due to airborne virus and evaluating whether this could be related to fomite transmission from contaminated bags as opposed to virus from contaminated PPE?

In the Controlled experiment, can you explain how the steady state concentration was estimated? What is the air exchange rate in the room, and how was this determined? Was the air filtered after experiments? What was the temperature and relative humidity, and this will affect aerosol sizes and the distances they travel?

In the statistical analysis, could Fisher’s exact tests be used to compare % positive across PPE type, exposure type, and location separately to look for statistically significant differences? That might be a nice addition to Table 1.

Related to a above comment, were there negative controls or field controls in addition to sampling the area for environmental contamination (in the environmental study, not the controlled study)? In other words, could the bags be contaminated with SARS-CoV-2 due to exposure to the air (aerosols or droplets) as opposed to or in addition to the PPE in the real-world environment? In the Discussion where the detection of SARS-CoV-2 on unexposed external surfaces of the paper bag is discussed, I think this is worth considering/mentioning. If this was not done, perhaps it is a limitation that could be mentioned – some insights into potential contamination via airborne or droplet spray in the controlled study but not in a real-world environment.

What was the limit of detection?

Figure 2 is interesting. If you stratify by PPE type or the type of aerosolizing procedure (or other potential confounders like facility type), do you see anything different? There appears to be a strong linear relationship for a certain set and no relationship with another.

In the Discussion where the controls are discussed, I think it’s important to distinguish between swab efficiency and transfer efficiency. The transfer efficiency of a gloved or ungloved touch of a bag is likely to be different than swabbing. Maybe a quick back-of-the-envelope example would be useful. Something like, “If we assume a transfer efficiency of ______% and ______ gc/cm^2 on the bag, only ______ gc would transfer to the fingertip (assuming 2 cm^2 of fingertip).”

Minor Comments:

In the Introduction where it’s said that HCWs face fomite transmission risk from “prolonged use” of PPE, I’m not sure what this means. Are you referring to things like hand-to-mask contact and, later, hand-to-face contact?

I like the Introduction – nice lead up to the objectives with a clear stated impact of the work, as well. The importance of fomite transmission is also not overstated, which I think is appropriate.

I think there’s a typo in the first subheading under Methods

Can the geographical location of the two regional urban hospitals be confirmed in the text? This might help if others do systematic literature reviews that include yours in their search.

I’m not sure what this means: “Surgical masks (ATSM level 3 mask) worn for over 20 minutes by a symptomatic hospitalized patient with a positive COVID-19 PCR test were included.” – Included as an AGP or included as samples? How are these samples related to the focus on PPE for healthcare?

Where it says all PPE was doffed and cleaned, does this refer to disinfection or just cleaning, such as wiping of with a non-disinfectant chemical?

Isn’t SARS-CoV-3 designated as BSL-3?

Figure 3 – Is it absorption of virus in the swab eluent or adsorption of the virus to the bag surface?

Reviewer #2: General Comments:

The work evaluates how effective of a barrier for fomite transmission of SARS-CoV-2 are paper bags storing masks, respirators, and face shields. Sampling (every 0.5 and 12 hours) for the presence of SARS-CoV-2 took place in the interior and exterior surfaces of paper bags. The processing included 177 swabs from 30 PPE samples. A low ~7% positivity rate was found among all samples and associated to ventilator disconnection causing exposure to bioaerosol from coughing. In conclusion, paper bags were not a significant fomite risk for SARS-CoV-2 transmission, suggesting that storing and re-using PPE when demanded with urgency is possible. Although the manuscript is generally well written and the methods and analysis appears appropriate, there are three major issues that should be addressed during a revision before the manuscript could be accepted for publication.

Major Comments:

1) The revised manuscript should increase the front size of Figure 1 to become readable after final professional editing for publication. It looks too small in the current form. Also, the current format of Figures 2 and 3 is not acceptable for publication and the figures should be recreated by plotting the data and exporting them with high resolution. The gray surrounding background should also be removed from Figure 2. Is there any statistical treatment for Figure 2?

2) For the Introduction section, the research is missing a connection to a key paper from the Health Planning and Management field that has escaped the attention of the authors but is facilitated here. The manuscript should have explained the work of Guzman (An overview of the effect of bioaerosol size in coronavirus disease 2019 transmission. Int J Health Plann Mgmt 2021, 36: 257-266. DOI: 10.1002/hpm.3095).

3) The conclusions are simply repeating statements summarizing the data that can remain in the revision. However, the manuscript should incorporate in the revision a deeper analysis of the outcomes of this work at the global level, for different settings and countries.

Reviewer #3: I would like to thank the journal and authors for the opportunity of revising the manuscript "Evaluating Fomite Risk of Brown Paper Bags Storing Personal Protective Equipment Exposed to SARS-CoV-2: A Quasi-Experimental Study".

The manuscript can be accepted for publication.

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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Evaluating Fomite Risk of Brown Paper Bags Storing Personal Protective Equipment Exposed to SARS-CoV-2: A Quasi-Experimental Study

PONE-D-22-12653R1

Dear Dr. Unger,

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.

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Kind regards,

Celia Andreu-Sánchez

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

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

Reviewer #1: Yes

Reviewer #2: Yes

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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

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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: Thank you for adequately responding to my comments and providing thoughtful responses. I don't have any further comments.

Reviewer #2: The work evaluates how effective of a barrier for fomite transmission of SARS-CoV-2 are paper bags storing masks, respirators, and face shields. Sampling (every 0.5 and 12 hours) for the presence of SARS-CoV-2 took place in the interior and exterior surfaces of paper bags. The processing included 177 swabs from 30 PPE samples. A low ~7% positivity rate was found among all samples and associated to ventilator disconnection causing exposure to bioaerosol from coughing. In conclusion, paper bags were not a significant fomite risk for SARS-CoV-2 transmission, suggesting that storing and re-using PPE when demanded with urgency is possible. The work has been improved after all comments from a previous version have been addressed. The work is recommended for publication in PLOS ONE.

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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

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