Updated for clarity, typos – some links added. 11:10 April 5th.
My opinion on this question has undergone a 160 degree shift in the last month. Not a full 180, because I did think wearing a mask would help in preventing community transmission and would remind the wearer not to touch their face. Still, I accepted the ‘idea from authority’ that face coverings, even N95 masks, would not offer much protection to the general public against the CCP virus. Those authorities, I’ve concluded, can’t distinguish absence of evidence from evidence of absence.
I’ve been working on this for several days while also tending to time critical spring gardening tasks. It’s still timely, even as the CDC has finally seen fit to slightly modify their advice on the wearing of masks as protection from the CCP virus.
I think they did not go far enough.
First, here’s the advice we’ve been given until yesterday:
CDC does not recommend that people who are well [is asymptomatic ‘well’?] wear a facemask to protect themselves from respiratory illnesses, including COVID-19. You should only wear a mask if a healthcare professional recommends it. A facemask should be used by people who have COVID-19 and are showing symptoms [The asymptomatic are not, of course.]. This is to protect others from the risk of getting infected. The use of facemasks also is crucial for health workers and other people who are taking care of someone infected with COVID-19 in close settings (at home or in a health care facility).
The Centers for Disease Control and Prevention (CDC) does not recommend that the general public wear N95 respirators [No. CDC said “facemasks.” As to N95s? The FDA is blocking their importation.] to protect themselves from respiratory diseases, including coronavirus (COVID-19). The best way to prevent illness is to avoid being exposed [Yes. Including everybody wearing a mask.] to this virus. However, as a reminder, CDC always recommends everyday preventive actions, such as hand washing, to help prevent the spread of respiratory diseases.
For the general American public, there is no added health benefit to wear a respiratory protective device (such as an N95 respirator), and the immediate health risk from COVID-19 is considered low.
Low? That’s why I can’t leave my house without a damn good reason? The FDA is as slow to update their website as they are on everything else.
In light of new [?] data about how COVID-19 spreads, along with evidence of widespread COVID-19 illness [“evidence of?” Yeah, I guess there’s some evidence.] in communities across the country, CDC recommends that people wear a cloth face covering to cover their nose and mouth in the community setting. This is to protect people around you if you are infected but do not have symptoms [Aha! They do know you may be asymptomatically infectious.].
It’s actually more than just protecting others, and face coverings should have been a general recommendation much earlier. Even a tiny percent success rate in preventing community transmission has non-trivial benefits.
Second, there is substantial evidence that using even less than perfect nose/mouth covering reduces potential virus ‘load.*’ The CDC is still not admitting this. If they had, it might encourage “hot spots” of infection to consider making wearing masks in public mandatory. (Laredo, Texas has done so.)
The biggest barrier to mask wearing may well be psychological – and the CDC reinforced Americans’ perception that only people with symptoms wear them. People who are considered incompetent to fit and wear an N95 mask are the same people expected to diagnose CCP virus symptoms – when many will be asymptomatic.
I get protecting the N95 supply for health care workers. I don’t get minimizing the protective value of even a scarf in order to do so.
That whole article is recommended, but I want to emphasize part of it as point 4, below. I’ve heard it said that even N95 masks aren’t that good against the CCP virus because the virus particle size is far below 0.3 microns. Four things about that,
- 1) They’re the best, affordable protection we have, or we wouldn’t be trying to preserve the supply for health care workers.
2) The virus is unlikely to be floating around as naked particles, it will be in a larger droplet. Even a scarf or bandana can help. Though see the Israeli Ministry of Health advice, linked below.
3) There has always been general agreement that masks cut down on infecting others; important because of some evidence that many** of those who contract the CCP virus are asymptomatic, yet still infectious. That means the amount of virus they might expel would not have to be reduced as much – by any sort of mask – to be protective for the wearer. Dose matters.
Reducing the virus load is protective.
4) In any case, N95s do filter particles smaller than .3 microns:
N95s are so-named because they filter out 95 percent of particles with a diameter of 0.3 microns, which are the most difficult particles to trap. Think of the filter in a mask not as a sieve but as a thicket—a dense tangle of minuscule filaments. To make it through, particles must flow seamlessly with air currents, weaving around every obstruction. Large particles are too heavy to pivot quickly, so they crash. Extremely tiny particles are buffeted by individual air molecules, bouncing about like pinballs and colliding with filaments. Particles 0.3 microns wide are just the right size to ride a stream of air through a filter’s fibrous maze, but it is still possible to thwart them with enough twists and turns.
Because N95s block the vast majority of particles that try to pass through them, they are formidable barriers against microbes. For context, the bacterium that causes anthrax is 0.8 microns wide and 1.4 microns long, whereas influenza viruses and coronaviruses are usually between 0.08 and 0.12 microns. But microbes expelled from someone’s respiratory tract are rarely naked: the droplets they travel in range in size from 0.6 to more than 1,000 microns.
It is not unreasonable to suspect that a mandatory mask policy would have cut down transmission at Mardi Gras in New Orleans, and the subways and Lunar New Year Parade in New York City. CDC knew this even as Bill de Blasio was encouraging people to assemble in parks via subway, and Nancy Pelosi was inviting people to the Lunar New Year parade in NYC.
Could it be as effective to mandate mask wearing in New York City, or Detroit, as it is to lock people in their houses – given high levels of non-compliance? It is easier to enforce than guessing whether some citizen is on their way to an essential job.
Because the general public is untrained in N95 mask fitting and use, they won’t get the same benefit a diligent health care worker does. Does that mean any mask is a waste of time? If it does flatten the curve, even if not as much as the lockdowns. If it does improve compliance. If it’s easier to enforce. If it got a few more back to work. Then, no, it’s not a waste of time. But everybody has to do it.
If we’re willing to put 10 million out of work, shouldn’t we have tried mandated masks? To the obvious objection, I’ll let Arnold Kling respond. Here:
[UPDATE: You want to object, “We can’t experiment with people’s lives in a crisis!” My response is that we are doing exactly that. We are experimenting with various lockdown policies, but not in a way that allows us to learn from the results.]
I do not like the way that the experts are dealing with this crisis. I am at the point where I don’t care about being charitable toward them. Nassim Taleb, who is never charitable to those who disagree with him, has a shorthand that I will modify for this purpose. Expert Yet Idiot, or EYI. [ASK is Kling’s askblog]
What should we rely on to make decisions?
ASK: rigorous studies and experiments
EYI: noisy data and models
What should we use to reduce the spread rate of the virus?
ASK: masks and scarves
What should government do to relieve individuals and small businesses?
ASK: provide backing for credit lines from banks
EYI: Massive intervention by the Fed and deficit spending
Other resources on the topic:
Slate Star Codex
Face Masks: Much More Than You Wanted To Know
Good overview. It’s comprehensive enough to justify the title. It does examine the question dispassionately, citing studies positive and negative.
Face mask shortage prompts CDC to loosen coronavirus guidance
This pretty much confirms surgical masks (which are not N95) provide some protection against the CCP virus. But, the public still shouldn’t be buying them, because health care workers should get them first, and there’s a shortage.
New York Times
More Americans Should Probably Wear Masks for Protection
Israeli Ministry of Health
Wearing a mask that covers your mouth and nose in public in order to minimize the chance of infection
Mask protocols ad including instructions on fabricating homemade masks.
As are some hospitals,
New York Times
Frightened Doctors Face Off With Hospitals Over Rules on Protective Gear
* Virus load is simply the quantity of viral particles. Exposure to fewer particles may still cause infection, but eventual symptoms seem to be proportional to the number of particles.
Mild cases have been found to have viral loads 60-fold less than severe cases (19) and it is likely that the viral loads of asymptomatic individuals are lower still, with possible implications for infectiousness and diagnosis.
New York Times
These Coronavirus Exposures Might Be the Most Dangerous
Both small and large amounts of virus can replicate within our cells and cause severe disease in vulnerable individuals such as the immunocompromised. In healthy people, however, immune systems respond as soon as they sense a virus growing inside. Recovery depends on which wins the race: viral spread or immune activation.
Virus experts know that viral dose affects illness severity. In the lab, mice receiving a low dose of virus clear it and recover, while the same virus at a higher dose kills them. Dose sensitivity has been observed for every common acute viral infection that has been studied in lab animals, including coronaviruses.
** Percent of asymptomatic people in 2 cases. Iceland’s testing has been rigorous. The Diamond Princess can be considered a petri dish test where humans were the agar.
50% were asymptomatic in Iceland. Note: this is an antigen test which reveals the presence of the virus. From the evidence that 50% of people who had an active case were asymptomatic we can infer there are people who have fully recovered who did not even know they were infected, and no longer host the virus. To identify them, a different test (for SARS-COV2 antibodies) is needed. If we knew who those recovered people are they could go back to work.
On the Diamond Princess cruise ship, “slightly less than half the passengers (48.6% ± 2.0%) who got the disease showed NO symptoms.”
CDC says it might be 25%:
As many as 1 in 4 people with coronavirus may not show symptoms, the CDC director warns