Should You Be Wearing a Mask in Public During Covid-19?

President Trump announced yesterday that the CDC is advising “the use of nonmedical cloth face covering as a voluntary health measure.”

The CDC website today states:

CDC recommends wearing cloth face coverings in public settings where other social distancing measures are difficult to maintain (e.g., grocery stores and pharmacies), especially in areas of significant community-based transmission.

CDC also advises the use of simple cloth face coverings to slow the spread of the virus and help people who may have the virus and do not know it from transmitting it to others.  Cloth face coverings fashioned from household items or made at home from common materials at low cost can be used as an additional, voluntary public health measure.

For a detailed and well-referenced article on the argument for wearing a mask in public I recommend this article ( Should You Wear a Mask in Public for Coronavirus? — Diet Doctor). 

Yes. Research shows that any barrier — tea towel, pillow case, vacuum cleaner bag — provides some protection and is better than nothing. The layer of fabric, or even paper, across the nose and mouth creates an obstacle to respiratory droplets, helping reduce the viral load that you either exhale upon someone else or they exhale upon you.

The article features this powerful graphic:

In addition to persuasive arguments for everyone wearing a mask in public, the article gives good information on mask creation and handling.

The CDC website  gives very detailed instructions on how to create the facial barrier at home and how to clean and disinfect them.

You can create one by sewing or non sewing methods. Helpful graphics are included:

You can also use a coffee filter and bandana to create a mask


Turbulent Gas Clouds


I became a believer in universal masking during Covid-19 after reading an article entitled “Turbulent Gas Clouds and Respiratory Pathogen Emissions Potential Implications for Reducing Transmission of COVID-19″ published March 26 in JAMA insights.

Figure 1 from that paper below shows a sneeze cloud projecting up to 8 meters.

The author notes

Recent work has demonstrated that exhalations, sneezes, and coughs not only consist of mucosalivary droplets following short-range semiballistic emission trajectories but, importantly, are primarily made of a multiphase turbulent gas (a puff) cloud that entrains ambient air and traps and carries within it clusters of droplets with a continuum of droplet sizes

Owing to the forward momentum of the cloud, pathogen-bearing droplets are propelled much farther than if they were emitted in isolation without a turbulent puff cloud trapping and carrying them forward. Given various combinations of an individual patient’s physiology and environmental conditions, such as humidity and temperature, the gas cloud and its payload of pathogen-bearing droplets of all sizes can travel 23 to 27 feet (7-8 m).

I’ve included additional comments from this paper at the end of this post for those with strong stomachs.

Universal Masking In Hospitals/Clinics

An opinion piece   published April 1 in  NEJM is less enthusiastic about the benefits of universal public masking

We know that wearing a mask outside health care facilities offers little, if any, protection from infection. Public health authorities define a significant exposure to Covid-19 as face-to-face contact within 6 feet with a patient with symptomatic Covid-19 that is sustained for at least a few minutes (and some say more than 10 minutes or even 30 minutes). The chance of catching Covid-19 from a passing interaction in a public space is therefore minimal. In many cases, the desire for widespread masking is a reflexive reaction to anxiety over the pandemic.

However, these authors feel that universal masking in hospitals may be beneficial for two reasons:

The first is during the care of a patient with unrecognized Covid-19. A mask alone in this setting will reduce risk only slightly, however, since it does not provide protection from droplets that may enter the eyes or from fomites on the patient or in the environment that providers may pick up on their hands and carry to their mucous membranes (particularly given the concern that mask wearers may have an increased tendency to touch their faces).

More compelling is the possibility that wearing a mask may reduce the likelihood of transmission from asymptomatic and minimally symptomatic health care workers with Covid-19 to other providers and patients. This concern increases as Covid-19 becomes more widespread in the community. We face a constant risk that a health care worker with early infection may bring the virus into our facilities and transmit it to others. Transmission from people with asymptomatic infection has been well documented, although it is unclear to what extent such transmission contributes to the overall spread of infection

Personally, I am convinced of the benefits of mask wearing and I will be wearing one when I go to my office.

Skeptically Yours,


N.B. More about turbulent gas clouds.

Importantly, the range of all droplets, large and small, is extended through their interaction with and trapping within the turbulent gas cloud, compared with the commonly accepted dichotomized droplet model that does not account for the possibility of a hot and moist gas cloud. Moreover, throughout the trajectory, droplets of all sizes settle out or evaporate at rates that depend not only on their size, but also on the degree of turbulence and speed of the gas cloud, coupled with the properties of the ambient environment (temperature, humidity, and airflow).

Droplets that settle along the trajectory can contaminate surfaces, while the rest remain trapped and clustered in the moving cloud. Eventually the cloud and its droplet payload lose momentum and coherence, and the remaining droplets within the cloud evaporate, producing residues or droplet nuclei that may stay suspended in the air for hours, following airflow patterns imposed by ventilation or climate-control systems

12 thoughts on “Should You Be Wearing a Mask in Public During Covid-19?”

  1. Though the illustration of case number trajectories is impressive, it is possible that (given that all the countries with mandatory mask wearing are in east Asia) there are other factors involved.
    My uneducated guess is that the take-home–that mask wearing in public is perhaps mainly benefitting others, and not so much the wearer. In any case, China learned after the SARS epidemic in 2003 that mask wearing is useful.
    The administration’s messaging on masks has been terrible, as discussed last week in the NY Times by Tufekci.

    1. We make uneducated guesses from our arm chairs while the administration has to be perfect on the front line. Smh.

  2. Dr Pearson my daughter gets our groceries and leaves them on the porch or in the it necessary to wipe everything off we make a solution to sterilize items with 3&1/4 cups of everclear alcohol and 3/4 cups of water mix up pour in spray bottles…What do your think value your opinion. Jim & Linda LeBold

  3. Much good information here. BUT the point u try make about the difference masks make is not so valid in my opinion. Those mask-wearing cultures and governments handled the issue much differently than here in the USA. The mask are likely a “correlate” and much less likely an effect for the improvements where mask were worn–as stated above. BTW, here is a corona virus summary update.

  4. Its more than just sneezes:

    /Users/lebow/Library/Containers/ Downloads/31C2D409-C12D-4AC6-8A2A-4793BF1B3BE3/Covid19TransmitExpiratoryParticlesEDITORIAL2020_AsadiS.pdf

  5. Perhaps now we can all wear burkas without comments and also defeat facial recognition cameras. It’s an ill wind…..

  6. I saw a picture of a child wearing a hat that had a clear plastic wraparound skirt extending almost to the shoulders.

    There was no filter involved, relying on air inhaled and exhaled via the gap at the bottom.

    A bit similar to my face mask when using my chain saw. The act of putting on this mask concentrates the mind on using the chainsaw VERY carefully. Same effect with wearing a mask against the virus.

    It would be very effective in stopping exhaled and coughed particles from spreading to others, but not sure whether it would prevent inhalation of particles exhaled or coughed by others.

    Fogging of glasses can be a problem with conventional masks, and this design looks to obviate that.

    Further testing of this plastic skirt design could be worthwhile, perhaps with a filter filling in the gap at the bottom, giving protection against inhaled virus.

  7. This study does give reasons to consider masks further. However, there are several shortcomings with this.

    First, it’s not directly addressing what I believe should be in question: namely, do masks prevent or mitigate the transmission of the virus. Of course, the primary goal in outcome is minimizing mortality, and you can only die from SARS-CoV-2 by contracting it. However, to answer the question that should be asked it would be more useful to look at mask usage and reported cases. This too has its own pitfalls as we have seen, as the amount of testing in each country differs fairly significantly and is not reflective of “actual” cases, although we need something to go off of for any meaningful analysis aside from testing everyone every day (which is clearly impractical if not impossible). That being said, the data suggests a correlation between countries that wear masks compared to countries that did not. And that would be the second point, that at best there is a correlation, which doesn’t necessarily imply causation.

    Many of the countries listed that wear masks don’t give an exact or approximate date when the mask wearing began. Even for the countries listed where dates are given you do not see much of an inflection point shortly after that date where the mortality rate begins to flatten. Also, there are varying degrees to which a country’s citizenry adhered to mask wearing.

    There’s another distinction worth noting: the Asian countries listed as donning the masks have somewhat of a culture of wearing masks and being mindful of contagions in light of the SARS outbreak in the early 2000s.

    There is more that I could say, but I’ll wrap it up with one last point on this for now. Knowing what we know currently regarding comorbidities, age, and mortality, comparing aging and sick western countries with relatively younger and healthier eastern ones bears further consideration. Also, different climates among countries. I’m certainly open to masks playing a role in mitigating the transmission of this virus, and a study like this is worthy of consideration. However, the first direct look at the transmissibility of the virus by those wearing masks cuts against the “common knowledge” that masks prevent spread of the virus by asymptomatic carriers. Hand washing, social distancing, and optimizing a populace’s immunocompetence are the most important of the modifiable risk factors.

  8. I’ll even add a study that needs to be seen for those saying the oft repeated “masks are to prevent you from spreading the virus” camp:

    I do note the small sample size, but it does not appear to provide the degree of prevention that people have assumed. Cotton and surgical masks may decrease the distance and viral load, but it shouldn’t make us that confident that they add a very significant layer of protection beyond hand washing and keeping a fair distance among most individuals

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