A Pandemic Early Warning System Decision Analysis Concept Utilizing a Distributed Network of Air Samplers via Electrostatic Air Precipitation

Round 1

Reviewer 1 Report

The entire methodology section seems to be missing citations. Sections of the manuscript, such as the description of the electrospray concentration and collection capability are basing the research on prior experiments and research methods, and therefore, should include numerous citations.

Lines 166-167 references observations made years ago, but does not include a citation to the work.

Overall, this trend of lack of citations is present throughout the manuscript.  This article reads as a review paper, analyzing currently available technology, and proposing potential uses.  While that is important, it is not clear that the work is novel, and it does not seem that there is adequate validation of the review, given the paucity of citations.

Author Response

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Reviewer 2 Report

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Comments for author File: Comments.pdf

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Reviewer 3 Report

This is an interesting concept paper. But the authors should consider the following challenges. Lines 109-110: Bacteria and viruses widely vary in size, and their agglomerates in the environments also rapidly change. How will this problem be handled during electrospray application? Is this equally effective in these size variation situations? Do you think this approach would work in ambient environmental conditions? Fig. 3: I suggest replacing this figure with much higher magnifications so that readers can see the spore morphology more accurately. This is unclear whether these spores are from Penicillium or Aspergillus. Penicillium spores in ambient air rarely exist in this form like long chains or so large agglomerates. How was this experiment conducted? Did you collect samples near an actively growing mold on some surfaces? Why are other spores missing here? Please provide more information. Line 177: This finding could be incorrect because electrospray was collecting both viable and non-viable spores, whereas an open culture plate was demonstrating only culturable spores in the form of colony counts. Again, please provide more information for this experiment conducted in ambient conditions. Did you use selective media for Penicillium? Line 185: The bacterial droplet concentrations during human breathing may not be so high. Please provide a good reference. Fig. 4: This figure is unclear. Only blue, pink, and one red dots are visible, and other colors are missing. Fonts are small and fuzzy. Please revise this figure. Line 196: This charge to mass ratio will vary for agglomerates of different sizes (from the same bacterial or viral species), and how will that problem be handled? Table 1: Please italicize all scientific names. You have provided information about individual bacterial cells but note that bacterial cells from active lab culture and ambient air under different environmental stresses may vary morphologically. Moreover, their agglomeration probabilities are largely unknown. How would these problems be handled? Lines 225 – 229: Mention their agglomeration-related issues here. Line 243: This type of decision tree is interesting but already known in taxonomic identifications. The reliability of the attributes is uncertain in different environmental conditions, and also, agglomerations between different species and other airborne particles are very likely, which may interfere with the attributes. Would these attributes work with the newly proposed instrumentation with electrospray? Why is staining involved then? Testing them individually for numerous bacterial species is almost impossible. How would this work for viruses with ultrafine size range and various shapes and surfaces? Provide more information on the feasibility of these decision trees in electrospray and optical sensor-based instruments. This approach sounds very attractive, but the feasibility is dubious. Figure 7: This type of clean surfaced bacterial cell is unlikely to be present in ambient air.

Author Response

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Round 2

Reviewer 2 Report

IN RESPONSE TO MY CONCERN ABOUT WHETHER NEUTRAL, NON-POLAR, NON-POLARIZABLE DEBRIS MATERIAL WOULD BE DISCRIMINATED AGAINST BY THE AUTHOR'S TECHNIQUE, THIS IS THEIR RESPONSE:

Polystyrene micospheres are not polarizable, but do carry a charge due to triboelectric effects, especially during the aerosolization process. This is why we used a P0-210 source to neutralize the charge of such spheres due to anything that we had done, and to create a background that would reflect a controlled simulation of a real world environment. While debris may be entrained due to kinetic collisions with desorbing electrospray droplets, we did not observe that they were attracted as much as a polar species will be.

VIRUSES AND BACTERIA WILL BE ENTRAINED BECAUSE THEY ARE EITHER POLAR OR POLARIZABLE. MEASUREMENTS OF M/Z AND Z WILL ESTABLISH THEIR MASSES. THIS IS ALL WELL AND FINE, BUT IT IS ALREADY KNOWN. THE ISSUE AT STAKE IS WHETHER THE PROPOSED METHOD WILL NOT CAPTURE THE SUPPOSEDLY MUCH LARGER LOAD OF AMBIENT DEBRIS PARTICLES.

IN MY VIEW, THE AUTHORS SHOULD DEMONSTRATE THAT, BEFORE THE PAPER IS ACCEPTED.

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Reviewer 3 Report

I am glad to see that the authors have appropriately addressed my comments and concerns. Regarding the comment on line 185 (of the previous version) I wanted to mean bacteria in droplets and they have responded to the point. Regarding Fig. 4, I would suggest they use the second one, which is clearer. A modified form of reCAPTCHA would be an interesting approach. Overall, this is a great concept paper and I am very excited to see the future outcomes. The authors requested my contact email address but I think this is a confidential review report and they may contact the editorial office for that.

Author Response

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Round 3

Reviewer 2 Report

As presented, particles of interest (viruses, bacteria, prions, etc.) are distinguished from debris in m/z mass spectra according to their masses, which are deduced from the simultaneous measurement of their charges. The assumption, then, is that the typical mass of debris particles is, I suppose, much larger than that of particles of interest. This caveat, if I understand correctly, should be added to the manuscript because it is essential to the concept.

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