I have a question about the use of facemasks by the general public. Is there any actual empirical evidence that the general use of facemasks reduces the contagion of the disease from the asymptomatic to a measurable extent? That the Chinese and South Koreans use them isn’t empirical evidence. It’s more akin to sympathetic magic.
James Frazer in his foundational book, The Golden Bough, summarized sympathetic magic like this:
If we analyze the principles of thought on which magic is based, they will probably be found to resolve themselves into two: first, that like produces like, or that an effect resembles its cause; and, second, that things which have once been in contact with each other continue to act on each other at a distance after the physical contact has been severed. The former principle may be called the Law of Similarity, the latter the Law of Contact or Contagion. From the first of these principles, namely the Law of Similarity, the magician infers that he can produce any effect he desires merely by imitating it: from the second he infers that whatever he does to a material object will affect equally the person with whom the object was once in contact, whether it formed part of his body or not.
I don’t doubt that the use of facemasks by medical personnel in hospital and, particularly, surgical settings reduces the spread of disease, both from the sick to the well but from the well to the sick. But the conditions of casual contact on the streets or in stores are quite different from those in hospitals and surgeries.
I don’t know about studies for face-masks as it’s not something I’ve researched. And I think it would depend on the type of mask.
But the theme of your post reminds me very much of this recent one from Scott Alexander, particularly section 3.
https://slatestarcodex.com/2020/04/14/a-failure-but-not-of-prediction/
I don’t recall the citation, and I’m in the middle of moving today so I’m not in a position to research it but I believe a study found quite a dramatic effect. I believe Steve referenced it in a comment. He may recall.
There is not a double blind, randomized clinical trial of masks vs no masks.
On the other hand; there are quite persuasive physical experiments that masks (even cloth masks) do block respiratory droplets that carry the virus coming out of an infectious person.
Given the minimal cost to masks — it passes the cost/benefit test. i.e. no one will die from wearing a mask.
Maybe the question is what are the cost / benefit for each intervention and where is threshold for demanding different levels of evidence.
That is, indeed, the underlying question.
I would add that rejecting one strategy as unscientific and then proposing another alternative which lacks a randomized controlled study is at the very least questionable and may even be nuts.
BTW Scott Alexander’s consideration of the facemask issue basically comes up what’s the harm? That fails to take into account cost or moral hazard. That’s why actual cost-benefit analysis is needed.
It may also bear mentioning that if your position is that if the Chinese, South Koreans, and Japanese do it, it must be effective or because evidence from China, South Korea, or Japan suggests it might have at least a marginal effect, why would you think that different measures taken in different parts of the same country might be warranted?
Lets see. Its OK to insist that we use HCQ, a drug that can kill you, without a study showing it works but it is not OK to use masks, that cant really hurt you? Anyway, yes there are studies showing that they reduce droplet spread and reduce disease spread. Anyway, link goes to an overview with lots of footnotes.
I would sum it up as follows. In the lab we see that droplet spread is diminished. Not eliminated but diminished. Next, when worn the way they should be worn they dont eliminate all risk, but reduce it. Last, if people dont wear them they dont work. In sum, if you want to reduce the risk to zero they dont work. If you want to reduce the risk in the 40%-50% range they work.
What is nice is that we have practical experience which is better than just having studies. With other respiratory disease this is what we have done when caring for pts and we have found them effective. (Also, did you see the chart showing the drop off in flu once we started social distancing, etc?)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4293989/
(Alexander notes in his opening comments that the evidence is strong that wearing a mask makes it less likely you will infect others. He then launches into this long, odd discussion that is mostly irrelevant. The question we want answered is if masks can help reduce the spread of disease. Yes, he has answered that in the first couple of paragraphs. He finally reaches that conclusion after flailing around. His conclusion follows. (Bear in mind he is a psychiatrist and this is not an area he will deal with.)
“7. Were the CDC recommendations intentionally deceptive?
No, and I owe them an apology here.
I think the evidence above suggests masks can be helpful. Masked health care workers were less likely to catch disease than unmasked ones. Masked travelers on planes were less likely to catch disease than unmasked ones. In per protocol analysis, masked family members are less likely to catch disease from an index patient than unmasked ones. Laboratory studies confirm that masks block most particles. All of this accords with a common-sense understanding of droplet and aerosol transmission of disease.”
Steve
The decision to use HCQ is optional (not “insisted†upon), and is one made between pt. and Dr. Like most drugs, there are side effects and precautions to be noted when patients have certain pre-existing conditions. Heart arrhythmias and retinal damage are two such HCQ side effects to be watched in people with heart disease and eye problems.
The VA trial using HCQ has become the latest news story, feeding more into the hazards of using this drug than it’s benefits. The 2 people who died after using this drug were considered to be very sick. There were also people in the same trial who recovered from the Coronavirus infection, after being administered HCQ.. However, little is made of this positive stat, as some experts tend to toss evidence of success into theâ€anecdotal†category which receives little medical recognition.
Wearing masks, unlike taking HCQ, has become mandatory, in some instances with a large fine attached for not complying. For most people there is no public option available to do otherwise, unless one wants to be subject to all the negative government induced consequences associated with having an unmasked face in public.
Some people see this as being onerous, while others promote it as practicing a consciousness towards maximizing safety.
My question was pretty much the opposite of that. I haven’t insisted that we do anything and I don’t object to people wearing masks if they want to.
I hope you understood what you did in your answer, steve. You did not answer my question and you did it angrily. I stipulated the effectiveness of masks in a medical setting, when worn by the symptomatic, and when encountering those with symptoms, especially in close quarters.
On May 1 Illinoisans are being compelled to don masks when venturing outside. That has costs associated with it in terms of the costs of the masks and in freedom and may not have a measurable effect on the spread of the disease.
I think social distancing may have a measurable effect. The evidence seems to support it. Will adding masks produce a measurable improvement?
Maybe the right analogy for masks is condoms to HIV.
They are both physical barrier interventions on the transmission of disease. While not fully protective; like condoms — masks should have a measurable effect on transmission.
I am not sure making mask wearing a law with fines is the right way for American society. Perhaps we should follow the “safe sex†approach — education and trusting people and non government entities to make the right decisions from that info.
After thinking about the analogies with HIV; I can see why Sweden went for their approach — even if it has not worked out so far.
“You did not answer my question and you did it angrily.”
I made a snarky comment and then I did answer your question. I cited some literature and I then went on to note that Alexander came to the same conclusion, masks help stop the spread of respiratory disease.
” may not have a measurable effect on the spread of the disease.”
If people dont wear them that is true but the evidence that they help reduce spread is pretty strong. As I said, we have years of experience with them and they help.
“The decision to use HCQ is optional ”
Dave’s question was as follows.
“I have a question about the use of facemasks by the general public. Is there any actual empirical evidence that the general use of facemasks reduces the contagion of the disease from the asymptomatic to a measurable extent? ”
So the issue is do we have evidence that they work, not do we want to talk about whether it should be optional. Having defined the question, why are you OK using HCQ for which there is no evidence, but questioning masks, for which there is a lot evidence? If you want to say “I know they help but dont think we should force people to wear them” that is OK and better than changing the topic.
Steve
I don’t know whether spread from the infected asymptomatic to the uninfected is impeded by masks in non-medical settings and neither do you. None of your examples address that question. Your anecdotal experience in medical settings is not relevant.
As I said I don’t oppose the voluntary use of facemasks but I do think that making them compulsory requires a higher level of proof than “it works in medical settings” or “what’s the harm”?
IT really comes down to whether spread is due to aerosol from breath or droplets from cough. sneeze, loud speech. Precious little research has been done regarding this.
https://quillette.com/2020/04/23/covid-19-superspreader-events-in-28-countries-critical-patterns-and-lessons/
“I don’t know whether spread from the infected asymptomatic to the uninfected is impeded by masks in non-medical settings and neither do you. ”
But we do know that spread from the infected people in the home setting, non-medical, is reduced by wearing masks with the flu. So it can work outside fo the hospital setting. Is there a double blind study showing that this will work on a large scale? Nope. Knowing what we know about mask wearing in other settings is there any reason to think it wont work. It looks like compliance should be the only reason it would not work. In every other setting tested masks helped, with he exception of the outpatient setting where they had less than 50% compliance.
So to be really honest I now doubt that it will be a real success. I have seen enough blog post like this one and enough articles go by email from the right wing press that compliance will be high.
Steve
But can’t reasonable people agree that it’s different talking to the grocery clerk across the atm and scale than it is to be cheek to jowls at a noisy ballgame yelling into your friends ear, or a noisy bar leaning across the table to get close to laugh and joke. Yet, my first example is where you most likely will see masks worn.