https://bmcinfectdis.biomedcentral.com/articles/10.1186/s128... [2019]
"In summary, despite the various mechanistic arguments about which organisms can be potentially airborne and therefore aerosol-transmissible, ultimately, the main deciding factor appears to be how many studies using various differing approaches: empirical (clinical, epidemiological), and/or experimental (e.g. using animal models), and/or mechanistic (using airflow tracers and air-sampling) methods, reach the same consensus opinion. Over time, the scientific community will eventually form an impression of the predominant transmission route for that specific agent, even if the conclusion is one of mixed transmission routes, with different routes predominating depending on the specific situations. This is the case for influenza viruses, and is likely the most realistic."
The link I posted is to a 2019 paper discussing how and why some viruses are considered airborne transmissible such that masks would help. (Single papers don't usually settle complex questions, right?)
cactus2093's links are to a paper discussing the difficulty of getting people to use masks correctly and a science popularization article describing an unnamed study from the University of New South Wales and an unidentified CDC study. The first link does include references about the utility of masks, to articles titled "Risk of transmission of airborne infection during train commute based on mathematical model", "Knowledge about pandemic influenza and compliance with containment measures among Australians", "Physical interventions to interrupt or reduce the spread of respiratory viruses: systematic review", "Professional and home-made face masks reduce exposure to respiratory infections among the general population", and "A schlieren optical study of the human cough with and without wearing masks for aerosol infection control", but those don't seem to imply the issue is settled. The second link does go on to say, "While some governments are already stockpiling masks for use in emergencies, MacIntyre said these guidelines had been implemented without evidence to support them. "We now have provided that evidence," she said," but it's difficult to evaluate the last sentence.
> Prior to 2020, most medical professionals believed most viruses, and corona viruses particularly, could not be transported as aerosols. This was a subject of research where the data had not come in.
cactus2093 replied
> I've also looked into it a little and come to the opposite conclusion. Here is one study from Singapore in 2014 that showed surgical and n95 have about a 68% and 95% efficacy respectively at preventing SARS transmission https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4293989/ Masks have also been shown to provide protection against the common cold (many strains of which are also coronaviruses) and seasonal flus https://www.livescience.com/7661-masks-protect-colds-flu.htm...
There's two ways I can see you interpreting this.
1) You are being extremely narrow in your focus and saying that you are talking specifically about viruses being transmitted as aerosols (although the overarching topic here is about whether or not masks are effective). And thus, since there was no research specifically about this, then there's no reason to recommend masks. This doesn't address the point that there's research that shows masks are effective against similar kinds of viruses.
2) You actually are talking about effectiveness of masks and saying that viruses could not be transmitted via aerosol was to say that because they are not shown to be transmitted via aerosol, then there's no evidence that masks would work, in which case, again, we're back to the issue that there was research prior to 2020 that showed masks are effective against similar kinds of viruses.
So the question remains, are you wrong about your assertion that
> Prior to 2020, most medical professionals believed most viruses, and corona viruses particularly, could not be transported as aerosols. This was a subject of research where the data had not come in.
and if not, what are we missing about what you're trying to say?
> Some kind of admission that the US health field ignored research because "eww, icky Asians?"
There was certainly the perception that Asians wearing masks was ridiculous. Whether or not this perception extended to American experts and influenced their conclusions is unknown to me.
"1) You are being extremely narrow in your focus and saying that you are talking specifically about viruses being transmitted as aerosols (although the overarching topic here is about whether or not masks are effective). And thus, since there was no research specifically about this, then there's no reason to recommend masks. This doesn't address the point that there's research that shows masks are effective against similar kinds of viruses.
"2) You actually are talking about effectiveness of masks and saying that viruses could not be transmitted via aerosol was to say that because they are not shown to be transmitted via aerosol, then there's no evidence that masks would work, in which case, again, we're back to the issue that there was research prior to 2020 that showed masks are effective against similar kinds of viruses."
Backing up a bit...
As far as I've seen, there are three primary routes for infection for respiratory diseases: 1) contaminated surfaces, 2) (large) droplets produced mostly by coughing or sneezing, and 3) (small) aerosol particles produced by normal activities like breathing and speaking.
The normal measures against 1) are avoiding touching possibly contaminated surfaces, washing your hands, and not touching your eyes, mouth, etc. And roughly speaking, that's about all you can do.
The normal measures against 2) are staying distant (i.e. 6ft) and keeping interactions short because the droplets do not remain airborne long, and covering your face when you cough or sneeze. Masks would certainly be helpful in the case of 2), but not especially so because a) the normal measures work fairly well, b) most people do not want to wear a mask[1], c) many people who do wear a mask do not do so correctly, and d) the supplies of medical grade masks were (are?) sketchy. (Both of the links provided are specifically aimed at b) and c), no?)[2] A study of 1000 students at an Australian university is interesting, but the advantage of a) don't necessarily overwhelm b), c), and d).
There are no normal measures against 3). The only useful measures are to avoid all contact with potential carriers, significantly improve indoor ventilation and air filtration (aerosols remain airborne for a very long time), and properly using medically-effective masks when interactions are required. Transmission by asymptomatic carriers is primary, hard epidemiological evidence of 3).
According to (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7322154/), asymptomatic carriers were reported at the end of January and significant confirmation appeared about March (https://wwwnc.cdc.gov/eid/article/26/7/20-1595_article). Shortly after that (April 3), the CDC recommended masks (https://www.bmj.com/content/369/bmj.m1422).
From your limited choices, my closest meaning is your 1). But,....
Now, put yourself in the place of someone making an official policy recommendation in, say, February or early March. You don't have hard evidence that masks are required, but you do understand that they will provide some marginal benefit. On the other hand, ensuring that masks are worn consistently and correctly is an uphill struggle (as we have seen over the last year). Further, the supply of medical grade masks where their use is required, hospitals for example, is not infinite. Oh, and you want to make the minimally invasive recommendation you can, because you actually aren't out to cause as much damage as possible by, say, killing the economy. Beyond that, you know that at some point you are going to be facing pandemic fatigue, where people stop taking the situation seriously and then things get very bad (as in last summer, last fall, and earlier this winter). What do you do?
As it turns out, they were wrong about some of their assumptions. Being wrong happens. It is not proof of an evil conspiracy or even of a conspiracy of stupidity. It's people who are pretty good at what they do, making what they think are the best choices, and being wrong.
Suggested Reading
https://www.bmj.com/content/369/bmj.m1422
https://news.ycombinator.com/item?id=25616014 (No, really, "The Plague Year" in the New Yorker is probably the best history of the pandemic so far, and explicitly touches on a lot of these issues---including medical professionals saying, "yeah, we were wrong.")
[1] I am talking about the US specifically, not Taiwan, Japan, or anywhere where mask wearing is more common socially.
[2] Everyone wearing pressurized, highly filtered contamination suits at all times would prevent essentially all cases of respiratory disease transmission. But no one is going to push that idea without a really, really good reason.
PS: While writing this, I ran across https://www.sciencedirect.com/science/article/pii/S019665532..., which is the first solid, halfway data-backed estimate of the prevalence of asymptomatic carriers: 1.82%
As I remember it, the advice wasn't "don't wear masks," the advice was "stay home." If they said "go buy masks," that would mean leaving your house to get a mask, which would directly contradict the more important advice of staying home. Also if they said wear a mask when you leave the house it would have been interpreted as "it's ok to go on with normal events as long as we have masks" which wasn't the message they were trying to send, either. The message was stay home, and at the time it was probably the right message, and not a lie.
There was “stay home” but also “stop buying masks because you are stopping medical, first responder, etc. personnel from getting them and they aren't useful for the general public” during the initial PPE supply shortage and hoarding.
This wasn't a lie, AFAICT, but Aa statement that was completely correct public health statement in the context it was given that was widely interpreted as an individual health statement.
There was no misunderstanding, the message was "don't wear a mask unless you're sick, masks don't help the wearer they only help keep a sick person from spreading it to others around them". That was just a lie at the time, we didn't know that for sure and we had every reason to suspect the opposite.
I've heard lots of people say that was the message, but it wasn't the one I heard and it's not the one I find in any of the documented statements from public health officials.
I've also looked into it a little and come to the opposite conclusion. Here is one study from Singapore in 2014 that showed surgical and n95 have about a 68% and 95% efficacy respectively at preventing SARS transmission https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4293989/ Masks have also been shown to provide protection against the common cold (many strains of which are also coronaviruses) and seasonal flus https://www.livescience.com/7661-masks-protect-colds-flu.htm...
In the absence of more specific information about SARS-COV-2 early in the pandemic, surely it would have made sense to default to using the preventative measures that were known to be effective at controlling SARS and other known respiratory diseases? Especially when these measures come with no real risks.
It's true that they didn't know with 100% certainty, and China's misinformation about human to human spread in the beginning and not allowing the CDC team in early to investigate certainly didn't help either. Maybe these experts, including Dr Fauci, the CDC, and WHO, just made what turned out to be very bad judgement calls and they honestly thought that masks wouldn't prevent the spread of the disease. But by far the likeliest explanation in my mind is that these institutions knowingly lied to the public in an attempt to manipulate people into not buying masks, and I still find that to be absolutely unconscionable.