Preprint Short Note Version 1 Preserved in Portico This version is not peer-reviewed

At “Half Mask” or “Nose Commando:” A Note Demonstrating Nasal Breaths Can Spread Microorganisms When Improperly Wearing a Mask During COVID-19

Version 1 : Received: 28 August 2020 / Approved: 30 August 2020 / Online: 30 August 2020 (11:41:33 CEST)

A peer-reviewed article of this Preprint also exists.

Wolff, R. J. (2020). At “half mask” or “nose commando:” A note demonstrating nasal breaths can spread microorganisms when improperly wearing a mask during COVID-19. Microbiologia Medica, 35(3). Wolff, R. J. (2020). At “half mask” or “nose commando:” A note demonstrating nasal breaths can spread microorganisms when improperly wearing a mask during COVID-19. Microbiologia Medica, 35(3).


Many individuals are wearing face masks improperly at ‘half mask’ and potentially breathing out microbes that can contaminate the air as well as anything below the nose. This note provides the first report that bacteria and fungi breathed out during nasal air exhalation are able to be cultured after landing on blood agar plates. The CFU’s are higher after both 10 breaths and extremely significant for 20 breaths compared to the control plates exposed to the air. Implications of this finding are that going ‘nose commando’ may be able to continue the spread of respiratory diseases such as COVID-19.


Mask; PPE; Bacteria; Nasal; Breath; Bacterial Culture; bioaerosols; COVID-19; SARS-CoV-2; hygiene behavior; face mask


Medicine and Pharmacology, Pulmonary and Respiratory Medicine

Comments (2)

Comment 1
Received: 15 September 2020
The commenter has declared there is no conflict of interests.
Comment: Sorry but this paper is bad even for a prepublished journal...
You say you were shocked when you see employees wearing a mask below the nose and breathing on the food. You know that before the pandemic nobody in food industry did wear a mask and everybody was fine with it? I didn’t also see remarkable studies saying food workers contribute bacteria and germs to customers. Also I never heard that Covid can be transmitted by ingested “infected” food (I always thought it were aerosols through the air captured with nose/mouth). Except perhaps the one who ate the first covid bat…

Also your paper is not the first demonstrating that bacteria growth from breath. Do more literature research. There is one from Berger et al describing a similar experiment with more people and better statistical outcome.
„Although mask placement below the nose was associated with higher mean colony counts than that above the nose, these differences were not statistically significant.“ Berger SA, Kramer M, Nagar H, Finkelstein A, Frimmerman A, Miller HI. Effect of surgical mask position on bacterial contamination of the operative field. J Hosp Infect. 1993;23(1):51-54. doi:10.1016/0195-6701(93)90130-r
Berger even has opposite results than you. There was no significant difference in wearing a mask below nose or above.

Also there are like dozens of articles that say that aerosols are NOT efficiently stopped by normal masks. Even the article from Scheuch you quote said:”Simple filter materials that are used in conventional surgical masks can hardly contribute to the separation of these aerosol particles (0,1-0,5µm).” or

“… the wearing of masks … would provide very little or no protection against the inhalation of virus associated with smaller particles, such as those in aerosols (<6 μm).” Donaldson A. Does wearing masks offer protection against viruses?. Vet Rec. 2020;187(3):119. doi:10.1136/vr.m3061 or
“We did not identify a significant effect of surgical face masks in reducing the amount of respiratory virus detected in coarse or fine particles in exhaled breath.” Cowling et al. Efficacy of face masks to prevent respiratory virus transmission: abridged secondary publication. Hong Kong Med J 2020;26(Suppl 4):S4-7

“Cloth masks were found to be ineffective for the whole spectrum of aerosol particle sizes and especially in SARS-CoV-2 virus most abundant size range.” Aerosol filtering efficiency of respiratory face masks used during the COVID-19 pandemic. Loupa, Karali, RAPSOMANIKIS medRxiv 2020.07.16.20155119;

Furthermore even the pro-mask scientists say that keeping distance is as important as wearing masks. “Therefore, the use of a mask does not provide complete protection, and social distancing remains important during a pandemic.” Dbouk T, Drikakis D. On respiratory droplets and face masks. Phys Fluids (1994). 2020;32(6):063303. doi:10.1063/5.0015044
“The cloth face cover is not a substitute for social distancing.” Yang et al. 2020, Chin.Med.J.

“From China's experience with novel coronavirus pneumonia, we know that social distancing is the most effective measure at present.” Qian M, Jiang J. COVID-19 and social distancing. Z Gesundh Wiss. 2020;1-3. doi:10.1007/s10389-020-01321-z
Perhaps do a study and watch people with and w/o masks if they keep distance at all.

Furthermore after the first lockdown research on the effectiveness of non pharmaceutical interventions was done and many said that school closings had a large effect, not masks.

“Among the five groups of NPIs considered, all were associated with statistically significant increases in PHR efficiency, except for the use of masks” “Further evidence is needed to assess whether enforcing the use of masks significantly improves overall PHR (public health response) efficiency”. Quantifying the efficiency of non-pharmaceutical interventions against SARS-COV-2 transmission in Europe. Garchitorena et al. medRxiv 2020.08.17.20174821; doi:

Also I am pretty sure that people wearing the mask under the nose will not infect dozens of other just by breathing (far to less viruses), there are even new studies that say that low virus amounts can provide you with some kind of variolation (Gandhi, NEJM 8.11.20)… so isn’t that a reason to allow people spread (low doses of) viruses with the (free) nose?
+ Respond to this comment
Response 1 to Comment 1
Received: 16 September 2020
The commenter has declared there is no conflict of interests.
Comment: [Response to Comment 1] While I do appreciate that you took the time to respond, including some useful information, but much misinterpretion, your tone and apparent anti-mask zealotry do limit the quality of your response. It would have been much more helpful to have a signed response with a more academic level of discourse.
Let me address some of your points:
Is it really so bad for me to be ‘shocked’ that people would think they are meeting a mask mandate while ignoring the function of the mask? Is ignorance that great, or are the people I saw just that uncaring about hygiene and trying to make a political statement such as “you can make me wear it, but I really won’t wear it to protect myself or others?”
“Nobody in the (sic) food industry did wear a mask and everybody was fine with it.” Nobody, everybody, I assume this means you do not work in food production or food preparation and so are speaking from lack of knowledge. Yes, while most in public areas did not wear a mask, it was partly because it was thought it would scare away customers. I strongly urge you to subscribe to “Food Safety” and industry journal which has had great concern for hygiene in both food preparation and production.
While released after my posting, but well before you replied, the CDC MMWR ( did publish a study indicating (with data) that people eating out had almost twice the risk of becoming infected.”
While we do not understand the impact of GI infection by COVID-19, there are dozens of studies indicating this occurs, and suggesting testing fecal residues (including waste treatment facilities) as a way to monitor the virus. Can the virus infecting the intestines move into the blood or other tissues – no information yet, but do not dismiss the possibility.
Also, while you said you thought aerosols were the only way to infection, you should remember that almost all early info and speculation were on the hands and transfer from touching the face, and all the ‘wash your hands’ propaganda that ignored aerosol transmission (and not recommending masks).
I appreciate your finding the Berger article which I did not find in my multiple searches for relevant studies. The article actually confirms my study (definitely NOT the opposite) having higher colony counts though their counts were not statistically significant (if they had been studying nasal exhalation). This is probably due to the use of less enriching media (do you have an electronic copy of the complete article to share? I have requested one). But it appears from articles citing them that they were actually testing for Staph from skin shedding, not exhalations from the nasal passage – so likely not relevant at all for my study.
The Donaldson article is a very short comment and does not provide any research refuting anything. In fact you missed the first sentence which says “There seems little doubt that the dispersion of Covid-19 droplets is reduced when people wear masks or face coverings.” It is also interesting that after giving data from a research article showing a 9.5 fold reduction in viruses inhaled while using a surgical mask, he then thinks this is an insignificant reduction? An almost 10X reduction of viruses inhaled seems very significant to me.
The Cowling study you cite you missed the nuances of the point and they actually say “We found that surgical masks were effective in preventing virus dissemination in coarse fraction of exhaled breath even when a participant coughed many times.” Yes, there are issues with the smallest fractions, but even some reduction could be helpful – and that corresponds with the following citation. Masks have had several systematic reviews and in general they have been found to reduce all respiratory infection rates, and this has held true for COVID-19 as well.
The Ghandi article is also a perspective and contains no new research. With the virus being so variable in apparent pathogenicity and without having any real clues about infectious dose, and no clear evidence of a proper immunity being developed (and maintained long term) it makes this wishful thinking, but something which should be looked at. It is more helpful to understand that all of our guesses and hypotheses should be carefully examined, not just condemned because they do not fit our biases. This article makes good points, and even states “Universal masking seems to reduce the rate of new infections.” And that is what we all want!
When you comment “Also I am pretty sure that people wearing the mask under the nose will not infect dozens of other just by breathing (far to less viruses [??])“ you appear to be stating your hopes, not any evidence. And your comments also miss the point that a food worker inhaling the virus, can get infected (up to 700 times more likely for olfactory cells), and then in later shifts spread the virus to customers and other employees. You also forget that people infect others back at home and other social situations, whether this is an infected customer or the employee. So can one food worker infect dozens (directly and indirectly)? Yes, these are called superspreaders! And they do exist, and many cases are related to the food industry.
And finally, yes it is critical that social distancing to be done, even required. But it alone will not be sufficient to stop the spread of this virus! And it cannot be completely followed as there are many situations when we need to be closer than 6 feet (and is that enough of a distance?).

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