Mask Confusion: Why the Change in Guidance and Under What Conditions do Masks Matter Most?

I see so much misunderstanding of this topic, I thought I would do my best to educate people on why the change in guidance on mask wearing actually made perfect sense even though the initial guidance also made sense (at the time). The CDC and Dr. Fauci have made many, many mistakes during this pandemic but I personally don’t believe the change in stance on mask wearing was one of them and as much as I really hate wearing them, I do see the logic in doing so indoors in public spaces, at least until we have better evidence to the contrary.

As you can see from the pic, at the start of this pandemic, the CDC and Dr. Fauci recommended against mask use for anyone not showing symptoms (March 8). The primary reason for this viewpoint was that only N95 masks (when worn properly) can guarantee that you will be protected from someone who is shedding it and there was (and still is) an acute shortage of those masks. So the conclusion at the time was why bother wearing a mask if it wasn’t going to keep you safe, especially when touching your face more as a result of wearing the mask could certainly increase your risk of catching the virus.

Now of course we all know that as of April 3, Dr. Fauci and the CDC are recommending mask use when in public. What happened in the 4 weeks between these two statements? Homemade masks still don’t guarantee you will be safe or keep the virus from spreading if you are asymptomatic. What’s the point in wearing one?

It is all about R (viral reproduction rate) and how we manage it from getting over 1. R is the number of people each infected person in turn infects. When it is significantly greater than 1, in the absence of any measures to contain it (like social distancing), infection numbers grow exponentially until herd immunity is reached. Unfortunately, the R0 for COVID-19 in a densely populated area (R0 is the R at the start of the epidemic when there are no interventions) is probably at least 3 and has been reported to be as high as 5.7). And no country has the hospital capacity to let the virus spread (without some measures to contain R) until herd immunity is reached. I have added a few links to peer reviewed publications that measure COVID-19 R. https://www.ncbi.nlm.nih.gov/pubmed/32349259 https://www.ncbi.nlm.nih.gov/pubmed/32164053 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7110798/?report=reader Also, in my review of the peer-reviewed literature it does appear that R estimates did not really come into clarity until mid to late March.

So what does R have to do with mask wearing? All the measures we are taking like social distancing and more extensive testing are designed to reduce the number of people each infected person in turn infects. Masks are just another tool in our arsenal to reduce R. Sure, masks are not fully protective but there is good reason to believe they going to reduce (not eliminate) the amount of virus that escapes into the air from an asymptomatic person’s nose/mouth and that should in turn reduce the number of people that asymptomatic person infects. Sure it doesn’t guarantee the asymptomatic person doesn't still infect someone to BUT it doesn’t have to, to be helpful. All it needs to do is reduce the rate of transmission a little and it can make a BIG difference in keeping that R near 1 and keeping the disease spread in check. The benefit is definitely much greater protecting the the asymptomatic person from shedding than it is protecting the uninfected person but it helps both ways. And we of course can’t be 100% sure we are uninfected unless you have COVID-19 antibodies (and we don’t know how long the immunity will last yet).

So why wasn’t this realized at the beginning of the outbreak? Perhaps it should have been but R is very difficult to measure in a new outbreak when diagnostic testing and antibody testing is in short supply and as a result, the high R for COVID-19 wasn’t fully appreciated until late March. In addition, it also wasn’t fully appreciated at the beginning of the outbreak how effective just breathing/talking would be in shedding viral particles and how long those particles remained airborne. This study in the top journal Nature was the first to rigorously look at the issue although they focused on symptomatic patients https://www.nature.com/articles/s41591-020-0843-2. It’s date of publication is April 3, the same day Dr. Fauci and the CDC changed their position. A couple week after that study, there was a study in the New England Journal of Medicine that received a lot of press showing that aerosolized COVID-19 virus remained suspended for several hours under laboratory conditions https://www.nejm.org/doi/full/10.1056/NEJMc2004973

That leads me to the other source of confusion. What do those laboratory studies really tell us because we don’t actually live in a laboratory? The “laboratory conditions” in the study I cited above dispersed the virus inside a metal sealed 10 gallon drum with no air circulation. Fortunately, we do not live inside unventilated steel drums but the research does suggest that the lower the ceiling and the weaker the ventilation the more that masks are going to help reduce R https://www.msn.com/en-us/health/medical/new-research-says-air-conditioning-can-spread-covid-19-but-its-more-complicated-than-that/ar-BB13h28W. The better the air flow and the higher the ceilings (and the better the ventilation draws air up and out), the less helpful masks will be in reducing R. Unfortunately ceiling height and airflow are not uniform in public places but until further research is done and minimum “safe” air flow standards established it is easy to understand the logic behind wearing masks inside public spaces, especially in light of the Nature publication. For more detail on how much virus we expel under various scenarios see this well sourced summary from a Professor at U. Mass https://www.erinbromage.com/post/the-risks-know-them-avoid-them?utm_campaign=Chris%20Kresser&utm_source=hs_email&utm_medium=email&utm_content=87885925&_hsenc=p2ANqtz-_oouquh4cOKVhrUBTPRWzBYZyyHZWrVQdvk53SVRW3wx-epjL3wqLkeyCv2HPAvxdxumqjJSwfaHFZ7FkVMFjD7x2lzytY4p_QCIjqA3k9P7mOlEY&_hsmi=87885925

To keep this balanced though, I should point out that there is still no compelling study performed in asymptomatic patients that truly measures the R reduction from wearing masks. I realize some of you will say until there is, I am not inclined to wear one but I wanted you to at least understand what drove the evolution of the thinking around mask wearing so the change itself isn't a barrier to wearing one. In addition, there is one recent compelling piece of (admittedly circumstantial) evidence that has convinced me I should wear a mask inside in public places until there is better data. That is the result of New York State antibody testing that show that essential workers (including healthcare workers, many of them which do not use N95 masks) have a LOWER rate of antibody positive tests than the general population. I have to agree with Cuomo on this one that this evidence is highly suggestive that indoor mask use is helping reduce R https://news.yahoo.com/cuomo-frontline-workers-tested-antibodies-162530547.html

Airflow when you are outside is a whole other story. There has been much criticism of the lab study cited above because conditions outside are nothing like they are inside. Even the lightest air current/wind has a tremendous power to disburse/evaporate droplets containing viral particles almost immediately after they leave the body. In other words, being outside is truly nothing like being inside a steel drum. It is highly likely you need to be standing very close to and downwind from an infected person for a mask to make a significant difference in reducing R. I hope that logic prevails and guidance on mask wearing in outdoor setting is ultimately much more relaxed compared to indoor setting but I also realize that may be a bit much to hope for…..This CDC post from last week gives me a little optimism though… https://thehill.com/policy/healthcare/496483-evidence-mounts-that-outside-is-safer-when-it-comes-to-covid-19…..

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Dr. Jeff Boschwitz has a PhD in Microbiology and Immunology and is currently an independent consultant helping healthcare business with growth and operations strategies.