The Science Behind Masks

One of the most frequent questions I am asked in these days of coronavirus is whether masks are beneficial.  So I lift pen to paper and will attempt to set down what is known from a science standpoint about the subject.  I don't know that it is terribly exciting, but I will do my best to cover the subject.

The Initial CDC statement.

I am not sure that most of us remember March of 2020 -- it was a month and a half ago (seems like longer) and Dr. Anthony Fauci and the CDC in lock step specifically recommended that individuals not wear masks.  This was in a time when other countries were specifically requesting their citizens to do so.  At this time there were two specific reasons given.

First of all, it was not thought that people who did not have symptoms of COVID-19 (fever, cough, etc) could pass the virus on to others.  If they did have symptoms they should just stay home and isolate.  The second reason was the personal protective equipment (PPE) was in short supply.  Hospitals and clinics across the United States were scrambling to try to get masks for their staff.  Many nurses and physicians were wearing masks for multiple shifts in a row.  There was a real fear that private citizens could buy up masks (just as they were doing toilet paper) and put healthcare workers at increased risk.

With these things in mind, the message was sent out clearly, "No masks for non-healthcare workers."

What We Know Today.

So a lot changes.  Obviously one of the things that has changed is that there is much less of a shortage of masks.  Hospitals and clinics are able to to get their hands on PPE for their staff.  I can change my mask after every office shift and don't have to use the same one a couple of times in a row, like I did in the beginning.

The second thing that has become clear is that most people with COVID-19 are most contaigious two to three days before they have symptoms.  This is based on a couple of studies done in both China and Germany:  https://www.sciencenews.org/article/coronavirus-covid-19-infection-contagious-days-before-symptoms-appear That seems to be why the average person with COVID-19 gives it to slightly under four other people.

The third thing is that while the virus is quite small, it is carried in droplets of water that are transmitted during breathing and speaking.  It seems pretty clear that these small droplets are how COVID-19 is transmitted.  https://www.pnas.org/content/early/2020/05/12/2006874117  These droplets probably remain in the air for quite awhile before they fall.  In many situations, particularly where singing or shouting are involved, droplets are probably projected much farther than the typically stated 6 feet mentioned in most social distancing mandates.  These droplets probably hang in the air for several minutes just waiting to be inhaled.  https://www.the-scientist.com/news-opinion/droplets-from-speech-can-float-in-air-for-eight-minutes-study-67538

The idea with masks is to reduce the amount of spread of water droplets filled with viral particles into the environment.  Obviously designs differ greatly, but this study:  https://pubs.acs.org/doi/10.1021/acsnano.0c03252  tested multiple fabrics and found that a dual cotton fabric mask was at least as effective as a surgical mask in halting the spread of the tiny droplets we are concerned with.  At the end, the study authors wrote, "In summary, we find that the use of cloth masks can potentially provide significant protection against the transmission of particles in the aerosol size range."

Different Categories

The WHO has now said that they don't think asymptomatic spread is very common with COVID-19.  This adds another layer of confusion on to everything.  Particularly when the CDC says that they think that 40 percent of transmission occurs in asymptomatic people.

What needs to be sorted out is that there are three categories of people who have COVID but don't seem to have symptoms.  (1) Asymptomatic People -- this is probably a good chunk of people who get COVID -- maybe 40 percent of individuals.  These folks never have any symptoms at all.  (2) Pre-symptomatic people -- these folks do not have symptoms now.  In four or five days, they will develop symptoms.  They certainly are shedding virus.  The only way to know the difference between these first two categories is to wait.  (3) Low Symptom COVID patients -- these are folks who don't realize that they have COVID at all, but in hind-sight, they will say, "Yes, I did have a stuffy nose and some sore throat a few weeks ago, but I thought it was just allergies."

These three categories of individuals tend not to stay home because they don't feel sick and can and do spread the virus.  This seen in this clarification by the WHO:  https://www.statnews.com/2020/06/09/who-comments-asymptomatic-spread-covid-19/

Many Countries Have Used Masks

Japan, Thailand, South Korea, and the Czech Republic all used masks aggressively early on to prevent spread of COVID-19.  They were able to do so with less aggressive business closings than were found in many US states.

Clearly this was not the only thing that these countries did.  Many had pretty robust testing and tracking programs in place too, but clearly the citizens in these countries were willing to wear masks and COVID was more easily controlled there.

Masks Seem to Act as a Crude Vaccine

This is a relatively new development, but it turns out the the severity of your COVID infection is related to the number of viral particles you inhale when you are exposed.  If you don't inhale very many, you may not get sick at all and your immune system can easily deal with them.  If you inhale lots and lots the infection is much more likely to be more severe.

Using masks seems to push the number of asymptomatic infections from 40 percent up to 80 percent of new infections.  Until there is a real vaccine, this may be a reasonable alternative.  Certainly I am in favor of anything that reduces hospitalizations, ICU admissions, and people on ventilators.  https://coronavirus.medium.com/can-masks-function-as-a-crude-vaccine-696049cb06db

Myths About Masks

I have read multiple times that masks cause decreased oxygen levels and elevated carbon dioxide levels in the users, but this simply isn't true in real world usage.  N95s are air tight and certainly could cause some reduction, but cloth and surgical masks are not air tight and should not reduce oxygenation in anyone wearing them.  Certainly, short term usage while shopping or other activities should not be an issue.  From a personal standpoint, I have checked my pulse ox at work while wearing a surgical mask and have not seen any change in my oxygen saturation. 

If you have really bad COPD and retain carbon dioxide and struggle with low oxygen levels, your experience might be different.  On the other hand, if that is your medical condition, you probably wouldn't do very well with COVID-19 either.

Some have said that masks collect the virus and then it somehow makes its way from the wearer's nose up into their brain.  Of course, this ignores the fact that virus is already in the mask wearer's nose (hence the odd loss of the sense of smell) and the fact that the oropharynx and the nasal passages are interconnected.  Quite simply though, you can't catch COVID from yourself and wearing a mask won't make it worse.

Then some people think that masks increase the chance that you will touch your face.  This may or may not be true.  People actually touch their face an amazing number of times each day, wearing a mask just makes you more aware of how many times you are actually touching your face.  Regardless, most transmission of COVID does not come from touching an infected object and then touching your mucus membranes, but rather from inhaling aerosolized COVID particles.   Most Covid-19 infections spread air

Honestly, reading this list of negatives, they come across as the list of someone who is trying to inflate the dangers of masks and not as real issues.  Health care providers have worn masks on a daily basis since the beginning of the pandemic without issues.  Surgeons operate with masks in place to protect their patients.

The biggest negatives in the real world are comfort and stigma.  That is to say, wearing a mask, when you aren't used to it is uncomfortable.  Most people can learn to wear them, but they don't necessarily see the need.  In addition, in the US, people are used to associating masks with disease and so it is felt that making them wear masks is akin to telling them that they are ill and identifying them as such to others.

From a public health standpoint, The Lancet came to the conclusion that combined with a hand washing and social distancing, it makes a lot of sense from a public health stand point:  https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30918-1/fulltext

The Unselfish Reason to Wear a Mask

Simply the point of wearing a mask is protect others from what you don't know you have.  If you knew for certain that you didn't have COVID-19, if for instance, you were tested once a week or something like that, you could go without a mask without endangering the people around you.

Wearing a mask is probably a more reasonable option for most of us.

The Selfish Reason to Wear a Mask

So, it seems as though a lot of people don't really care about whether they transmit the virus to others.  The people who die will mainly be old people -- or people with prior medical problems, so no big deal (I am writing sarcastically).

Even if you don't believe the virus is a big deal and the only important thing is getting the "economy back on track," the best way to do this is to cut down on asymptomatic spread of the virus.  This preprints article:  https://www.preprints.org/manuscript/202004.0203/v1  indicates that if masks were 50 percent effective (a very conservative estimate) at reducing the spread of the virus, they would make a huge impact.  That is to say, normally over a month's time you would normally see 100 cases spread to 30,000 people with no intervention, however with a 50 percent reduction in viral spread with masks, that could drop to around 600 cases.

In addition, masks probably mean fewer serious infections and more mild or complete symptomless cases.

What this means, pure and simple, is that countries that adopt masks should be able to have fewer restrictions on behavior and have them for shorter duration.  That, to my way of thinking is a good thing.

I suppose I am like most people.  I want things to get back to normal as quickly as possible and to me, masks are an effective and inexpensive way to make this happen.  Countries that have used them have had very good results and no downsides.