Science-Blind: Opinions based on research vs personal

[.Scott]

I live in Pelham, NH - where COVID-19 is almost, but not quite, under control.
And I have been talking to people who oppose using masks - or only use it because of social pressure.

At this point, my "N" is only about 5. But there seems to be a pattern. They are people who never really made it through High School - either dropping out, dropping out of classes, or are from school districts known to have bigger problems than getting kids educated. And they don't seem to differentiate statements from research as inherently different than statements from (for example) Trump.

Needless to say, in the COVID-19 environment, this blindness can be very consequential.

My thought is that we need hands-on evidence-based exercises starting in roughly grade 3. Kids need to know where science comes from in a very personally-connected way. It isn't good enough that they be told that research is done - they need to do some themselves, collect the results, and perhaps even have it peer reviewed.

 

[Vanadium 50]

Is there evidence that masks help given that other actions (social distancing, hand washing, minimizing contact with others) are taken? I believe there is not (and such data would be quite hard to get) and the argument for masks is "it stands to reason" and the costs are low.

If not, it's hard to say anti-mask is anti-science. It (anti-mask) is probably wrong, but that doesn't mean it's anti-science. It is certainly anti-scientism and anti-expert.

There is also a non-science based pro-mask story. Airlines used to stop selling middle seats. Now they do, but require mask usage. They say this is for Covid safety. That's not what science says.

 

[.Scott]

Is there evidence that masks help given that other actions (social distancing, hand washing, minimizing contact with others) are taken? I believe there is not (and such data would be quite hard to get) and the argument for masks is "it stands to reason" and the costs are low.

I think this study is really critical:
Medrxiv Preprint (preprint)
News Medical (news coverage)

What makes that study interesting is that they collected samples from 2 hospital rooms with inactive, seated COVID-19 patients, collected aerosol from the air at a distance of 2m to 4.8 m with a wet surface, and then used that to infect cell cultures. It shows the full transmission path in a situation where social distancing and hand washing were not factors.

I have not found a SARS-Cov-2 study with this same kind of full path coverage for either fomites or droplets.

Let's look very closely at this "hand washing" thing...
I'm sure you've read about how long SARS-Cov-2 remains viable on plastic, paper, and stainless steel (hours to days). But when it comes to hand washing, there is a critical piece of information that is not being well advertised.
SARS-Cov-2 is a virus that encapsulates itself in lipid:
Pubmed: Influenza - 5 minutes
Science Direct: Influenza - upto 30 minute, but less when droplet integrity was not sustained.
If you suspect you just touched something contaminated with SARS-Cov-2 and you don't have ready access to hand washing supplies, I would rub my hands together (to force contact between my skin and the virus) and then be careful not to touch your face for the next 5 to 10 minutes. To be clear, alcohol or soap are much better - they can kill on contact.

Here is an article with lots of citations:
Masks work
In particular:

Evidence from laboratory experiments, hospitals, and whole countries shows that masks work

(their links to the citations)

Certainly minimizing contact with others is important - but the people I was talking to weren't doing that. And "minimizing" hardly means eliminating. I have found no good replacement for shopping at a grocery store.

Social distancing and hand washing are important - but the people I have talked with were also the ones willing to shake hands. And none of the super-spreader events can be explained by fomites.

 

[Vanadium 50]

I think this study is really critical:

That study shows , well, suggests - the word "mask" appears nowhere in the paper - that masks by themselves would be effective in certain cases: cases that most closely mimic the hospital ward studied. (e.g. a subway car would be closer than a grocery store) But it doesn't address whether masks make any difference to people already taking other steps (probably some) and whether it's significant (arguable: if my odds of dying of it go from 10^-5 to 10^-6 is this significant? Some would say, yes, it's a factor of 10. Others would say no, it's 0.0009%.)

I don't think you've changed my mind. It may be wrong to decide masks are largely unhelpful, but it isn't unscientific.

 

[.Scott]

Hello @Vanadium 50 :
If I am going to take you as #6 in N=6 (which you seem to be volunteering for), I need to ask this qualifying question: Do you oppose using masks - or do only use it because of social pressure? If not, then you are not a case in point. If so, then you are an outlier - and I would like to hear your thought process on this.

That said, it was not my purpose to convince anyone that wearing a mask is useful. But if you look at those other links I provided, there is certainly ample evidence. That hospital study should be taken for what it was intended - a procedure that covers the objections many had about whether the virus can be communicated with aerosols under "normal" conditions. Certainly those hospital rooms were representative of many indoor areas that people visit.

But there are other studies (that I cited directly of indirectly above) that show populations that have worn masks are better off than those not wearing masks. If you are looking to avoid COVID-19, wearing a mask when indoors with many others is certainly playing the odds.

 

[vela]

At this point, my "N" is only about 5. But there seems to be a pattern. They are people who never really made it through High School - either dropping out, dropping out of classes, or are from school districts known to have bigger problems than getting kids educated. And they don't seem to differentiate statements from research as inherently different than statements from (for example) Trump.

Ignorance can certainly play a role in this sort of behavior, and education may help alleviate that in part. People need to learn how to think critically, and they need a certain baseline of knowledge so they can evaluate whether sources or claims are credible or not.

But even then, I fear that the problem goes much deeper than that. I have a friend who is an anti-vaxxer. She's quite intelligent, but there's no amount of scientific evidence that will persuade her that vaccines work. Anything that is pro-vaccine is part of a Big Pharma conspiracy, and anything anti-vaccine is obviously true because it's from "real" people. How do you combat that sort of willful ignorance?

To me, COVID-19 appears to be more like the anti-vaccine situation because the disease has been politicized. Simple ignorance can make some individuals more susceptible to fallacious arguments, but I think it goes quite a bit beyond that. Reason doesn't matter. Which tribe you belong to does.

 

[gmax137]

I wear a mask in public because
1) the Governor (Nevada) is threatening businesses that allow their customers to go maskless
2) I think the more people are seen wearing masks, the more some otherwise skeptical people will think maybe they should take the virus seriously

My mask-wearing is not an effort to protect myself. I'm not sure if mask wearing really protects other people. Even now, six months in, I see people with their noses sticking out, I see people scratching their noses/faces under the mask, I see people sneezing (hard!) without covering up in the crook of their arm.

Not sure if that makes me your N=7. I am not a high school dropout.

 

[Vanadium 50]

Do you oppose using masks - or do only use it because of social pressure?

I think it's not so clear.

(1) Masks should not be thought of as the primary means of protection. They are probably #4 or #5, and are certainly not an excuse for avoiding #1-3 because "it's OK, I have a mask". Situations like airlines unblocking seats but requiring masks are likely making this worse, not better.

(2) In many cases, mandating a mask will produce a small, perhaps zero, advantage over recommending a mask.

(3) There is an element of social pressure on both sides.

(4) The thought processes that lead to rejecting masks are not necessarily anti-science. The thought processes that lead to accepting them are not necessarily pro-science.

 

[hutchphd]

The thought processes that lead to rejecting masks are not necessarily anti-science. The thought processes that lead to accepting them are not necessarily pro-science

How about a discussion based upon risk-benefit both personal and societal. The science is admittedly slightly undercooked, but pandemics are messy . I see no reasonable risk-benefit analysis that argues for not wearing a mask.

 

[Vanadium 50]

The science is admittedly slightly undercooked

Then people who come to another conclusion than the OP are not anti-science. They may still be wrong.

However, using public resources to go after some farmer not wearing a mask in his fields miles away from the nearest case seems like a waste.

 

[.Scott]

(2) In many cases, mandating a mask will produce a small, perhaps zero, advantage over recommending a mask.

In New Hampshire, the "Live Free or Die" State, with one exception we have only "guidelines" from the Governor. The exception was enacted earlier this month (August) - everyone at a “scheduled gathering” of 100 or more people must wear a face covering.

On the other hand, if you walk into a store with no face mask, you will be noticed.

So far, the results have been good. On https://covidactnow.org/, only Vermont has had consistent numbers better than New Hampshire. (At the moment, no State is considered "green").

There have definitely been cases where things went too far. There was a video of a ship coming into port with passengers lining the rails - no social distancing and no masks. The situation was widely condemned - but really, they were along the rails, a one dimensional formation and the wind + ship velocity was well over 10 knots. So there was no real chance of communication - especially any sort of super-spreader event.

On the other hand, I think the Biogen meeting in February is a local story that has world-wide attention. It was a 2-day gathering of 200 people which resulted in an immediate 90 infections and ultimately 20,000 world-wide.

 

[hutchphd]

Then people who come to another conclusion than the OP are not anti-science. They may still be wrong.

However, using public resources to go after some farmer not wearing a mask in his fields miles away from the nearest case seems like a waste.

Might still, be wrong? What does wrong mean?
There is a very small possibility they may be scientifically correct.

They are still morally reprehensible. Cost-benefit.

 

[Vanadium 50]

Who is morally reprehensible? My putative farmer? I disagree. Airline execs? I might agree.

 

[atyy]

There is also a non-science based pro-mask story. Airlines used to stop selling middle seats. Now they do, but require mask usage. They say this is for Covid safety. That's not what science says.

Are you saying this because airlines only require cloth masks and not medical masks? Medical personnel wear masks (and other protection) that is effective. If airlines require the same protection as what medical personnel get, couldn't it be safe to sell the middle seats?

 

[atyy]

That said, it was not my purpose to convince anyone that wearing a mask is useful. But if you look at those other links I provided, there is certainly ample evidence. That hospital study should be taken for what it was intended - a procedure that covers the objections many had about whether the virus can be communicated with aerosols under "normal" conditions. Certainly those hospital rooms were representative of many indoor areas that people visit.

It is unclear what you mean by "representative". There was a confirmed case in each room. The probability of being 4 meters from a case depends on where you are. Also, the paper doesn't say whether the cases were symptomatic or asymptomatic. And the air samplings were for 3 hours.

Incidentally, the current WHO recommendations for masking by the general public are for when safe distancing cannot be maintained, so there is no consensus that masking should be required if safe distancing is possible. Of course, I do advocate following your local laws, but there may be other considerations behind the laws that are not purely scientific.

 

[Vanadium 50]

If airlines required passengers in full hazmat suits we could discuss that. But they don't. Instead they jam as many people on a plane as they can, so long as there is some kind of lint on their face.

Because science.

 

[.Scott]

It is unclear what you mean by "representative". There was a confirmed case in each room. The probability of being 4 meters from a case depends on where you are. Also, the paper doesn't say whether the cases were symptomatic or asymptomatic. And the air samplings were for 3 hours.

Incidentally, the current WHO recommendations for masking by the general public are for when safe distancing cannot be maintained, so there is no consensus that masking should be required if safe distancing is possible. Of course, I do advocate following your local laws, but there may be other considerations behind the laws that are not purely scientific.

According to the paper, the patients were lying. Though they were symptomatic with risk factors, they were not coughing at that time.

Except for the patient being quiet, the situation is certainly similar to many indoor meetings that have become known as super-spreader events.

 

[.Scott]

Hello @atyy :
I just took a look at that WHO video. It is an excellent example of a very bad COVID-19 story line - and I thank you for it. In general the bad story line goes something like "as the COVID-19 case numbers go down, things will get easier for the public". To be sure, things will get better at hospitals, but things will get more involved for everyone else.

There are two issues: the individual likelihood of someone contracting COVID-19 (bearing directly on individual health), and the community infection rate (bearing directly on the threat to the economy and community services).

I will take my town as an example. There are currently 4 known cases in Pelham - a town of about 14,000. The New Hampshire positive test rate is 1.1% and by most standards we have ample tracing staff for the known cases. So the actual number of cases in Pelham is probably more than 4, but not much more - maybe 6 or 7 - and we would hope that most (or all) of them are keeping themselves secluded.

So, from an individual health point of view, you could argue that with a lessened threat, you can apply lessened standards - exactly what is advocated in that WHO video.

But "individual health" is not the sole objective. The objective is to bring the economy online in full - and to do so while keeping the infection rate well below 1.0. We want everything, and we want COVID-19 community resilience. By community resilience, I mean that if we are suddenly burdened with a super-spreader event and another 200 COVID-19 cases are created, those cases will dwindle to nothing within a month or two - that would be an infection rate of roughly 0.60.

In order for this to happen, we start with stay at home (easy) and we move on to do more in new ways. The final result is an accumulation of practices that allow us to do everything we want while keeping the infection rate very low. We should be accumulating COVID-19 accomodations until we reach our goal of doing everything safely. We need to be accumulating these accommodations - not dropping them.

 

[atyy]

According to the paper, the patients were sitting quietly - not speaking. Though they were symptomatic (otherwise they would not have been in the hospital), they were not coughing at that time.

Except for the patient being quiet, the situation is certainly similar to many indoor meetings that have become known as super-spreader events.

Are you referring to this paper: https://www.medrxiv.org/content/10.1101/2020.08.03.20167395v1 ?

If both patients were sitting quietly, why do they draw them lying down in Fig. 1?

 

[atyy]

If airlines required passengers in full hazmat suits we could discuss that. But they don't. Instead they jam as many people on a plane as they can, so long as there is some kind of lint on their face.

Because science.

A cloth mask is probably not enough, but I would like to know how much below a full hazmat suit one would be ok. I'm pretty sure an N95 mask and goggles would be fine (say for a trip NYC to San Francisco), if the person next to you were asymptomatic and wearing a cloth mask. But what about just a surgical mask, if the person next to you were asymptomatic and wearing a cloth mask? Available evidence suggests that it is hard to show that N95 masks are more effective than surgical masks, although we clearly expect that to be the case: https://www.acpjournals.org/doi/10.7326/L20-0175.

 

[.Scott]

Are you referring to this paper: https://www.medrxiv.org/content/10.1101/2020.08.03.20167395v1 ?
If both patients were sitting quietly, why do they draw them lying down in Fig. 1?

You're right. I have read so many COVID-19 studies and articles this year, I am mixing them up.
They show two subjects - both lying down - one prone, one face up.
Interestingly, one would have been expected to be quite infectious and the other not nearly so infectious:

Patient 1 was a person with coronary artery disease and other co-morbidities who had been transferred from a long-term care facility for COVID-19 treatment the evening before our air sampling tests were initiated; he had a positive NP swab test on admission that was positive for SARS-CoV-2 by RT-PCR. Patient 2 had been admitted four days before the air sampling tests with a mid-brain stroke; the patient had a positive NP swab test for SARS-CoV-2 on admission, but a repeat test was negative, and the patient was in the process of being discharged at the time the air sampling was being done.

 

[.Scott]

A cloth mask is probably not enough, but I would like to know how much below a full hazmat suit one would be ok. I'm pretty sure an N95 mask and goggles would be fine (say for a trip NYC to San Francisco), if the person next to you were asymptomatic and wearing a cloth mask. But what about just a surgical mask, if the person next to you were asymptomatic and wearing a cloth mask? Available evidence suggests that it is hard to show that N95 masks are more effective than surgical masks, although we clearly expect that to be the case: https://www.acpjournals.org/doi/10.7326/L20-0175.

I don't know how critical the length of the airline trip would be. The time waiting on the ground - in the jetway or cabin - would be my first concern.

During the actual travel, cabin pressure is kept at about 8000 ft msl and the FAA requires ventilation of 0.55 pounds of air per passenger per minute. At cabin pressure, that's about 250 liters per passenger per minute - and I have been on flights where this was far exceeded.
I still wouldn't want to be seated next to a Covid patient - but the opportunity for "superspreading" would need to be investigated specifically for air travel. Nothing else would be similar.

 

[atyy]

You're right. I have read so many COVID-19 studies and articles this year, I am mixing them up.
They show two subjects - both lying down - one prone, one face up.
Interestingly, one would have been expected to be quite infectious and the other not nearly so infectious:

So in fact it was only 1 patient (not 2) then from whose room air they managed to get viable virus. I don't see that the patient wasn't coughing during the time they collected the sample. And it seems they collected for 3 hours?

 

[Andy Resnick]

My thought is that we need hands-on evidence-based exercises starting in roughly grade 3. Kids need to know where science comes from in a very personally-connected way. It isn't good enough that they be told that research is done - they need to do some themselves, collect the results, and perhaps even have it peer reviewed.

Presumably this is your central hypothesis. Unfortunately, it's also disconnected from reality- have you ever seen 3rd grade science projects? Not ones done by parents- actual 3rd grade work. Americans, in the main, don't value expert advice and prefer instead to 'figure it out for themselves' and thus equate opinion with knowledge.
The rapidity with which this thread went off-topic is evidence enough of this. I was not aware PF was inhabited by so many public health experts.

 

[atyy]

Here is an article with lots of citations:
Masks work
In particular:
(their links to the citations)

It is a speculative piece. One piece of correlative evidence cited via a link https://link.springer.com/article/10.1007/s11606-020-06067-8 is weak - that mild cases correlate with universal masking in Singapore. In Singapore, universal masking started after the beginning of a sharp rise in confirmed cases. The onset of universal masking came after the implementation of quasi-lockdown like measures. In both the early phase of the sharp rise (before universal masking) and the late phase, the rate of severe cases remained low, and it is not clear whether there is a difference in rates of severe cases between early and late phases. So it is unclear whether universal masking caused the infections to be less severe.

 

[.Scott]

So in fact it was only 1 patient (not 2) then from whose room air they managed to get viable virus.

The paper describes two patients - and shows two patients in the diagram.

 

[atyy]

The paper describes two patients - and shows two patients in the diagram.

But from how many rooms did they manage to cultivate virus from sampling the air? One, or two?

 

[.Scott]

But from how many rooms did they manage to cultivate virus from sampling the air? One, or two?

It was one room (with a divider), two patients, two collectors.
There was one collector and one patient on either side of the room divider.
Apparently, the divider was not entirely effective at blocking the virus, because patient 2's collector was still picking up SARS-Cov-2 (at 16 particles per liter) after patient 2 was discharged.

 

[atyy]

It was one room (with a divider), two patients, two collectors.
There was one collector and one patient on either side of the room divider.
Apparently, the divider was not entirely effective at blocking the virus, because patient 2's collector was still picking up SARS-Cov-2 (at 16 particles per liter) after patient 2 was discharged.

It looks to me like they did not get any live virus from Patient 2, who was negative. The live virus was from Patient 1, the active case.

I don't see them say anywhere that Patient 1 was not coughing during the collection.

Also, I don't see them exclude that Patient 1 got up and walked near the collecting device during the collection.

Is the bathroom shared between Patient 1 and Patient 2?

 

[Dr. Courtney]

It's easy to say that a mask meeting some standard helps if "all other factors are equal."

But that ignores the reality of human behavior. Most of the folks I've seen with masks are touching their faces every few minutes.

Some ground may be gained by masks regarding transmission via air. But how much ground is lost through contact transmission?

Me? I like distance. I like hand washing. I like not touching common objects. Do those things, and I don't think a mask helps. Don't do those things? I don't think a mask will make much difference.

But none of the mask mandates I've seen for public use even meet any given standard. I could wear any bit of cloth over my face, and so could anyone else.

So my household is putting more stock in reducing face-to-face social interactions by over 90% and keeping 6 feet away when we do go out.

 

[PAllen]

On the other hand, I am highly skeptical of surface transmission. Someone sneezes near a surface and it gets contaminated. Virus starts degrading at a steady rate. Someone touches the surface getting, say, 1/10 the viral load in the air near the surface at the time of the sneeze. Then, they scratch the outside of their nose, inhaling at the same time, say another tenfold reduction in viral load. Thus, compared to inhalation of aerosols near where someone recently sneezed, you have 100 fold reduction in viral load for the multistep touch transmission. Note, no amount of viral load on your hands will matter unless you touch your nose or mouth (possibly, but unverified, eyes) before washing your hands or waiting for the virus to degrade. Epidemiologists have so far documented no case whatsoever of coronovirus transmission primarily by surface touching. And of spread by droplet/aerosol inhalation, indoor cases outnumber outdoors by 50-1.

In my view, the best evidence supports the following:

1) indoors, the most critical thing is near universal mask wearing because aerosols can last an hour or more and distance is minimal protection. Evidence: detailed analysis of restaurant transmission, where adjacent tables as well as tables 20+ feet away connected by air flow patterns were the ones affected. Distance is the next most important factor. Mask wearing has to be near universal because the weaknesses of non ND95 masks are minimized if all parties wear them (at least covering nose and mouth).*

2) Outdoors, mask wearing is largely irrelevant unless people are a few feet or less from each other for many minutes, or (equivalently) there are a very large number of close contacts in a relatively short span of time.

Inhalation of droplets or aerosols is the only confirmed mode of transmission.

* Let's think about some basic physics of a mask that at least reasonably covers nose and mouth, but is not high tech. On inhale, negative pressure seals the edges reasonably well, on exhale (or sneeze) they open. With both wearing masks, these effects compensate to reduce viral load inhaled. Note, I have verified by my own experiments with chilled slides that all masks other than professionally fitted ND95 leak significantly on the edges on exhale, putting a lie to the oft quoted claim that they protect others more than you. However, epidemiologists are now more and more agreeing with the idea that for indoors protection when others are not wearing masks, the only adequate protection is an ND95 mask, irrespective of distance; and that otherwise, best bet for indoors is universal mask wearing as long as coverage is from bridge of nose to below chin (and distance doesn't much matter indoors, because of how far aerosols can travel before they dissipate).

 

[atyy]

1) indoors, the most critical thing is near universal mask wearing because aerosols can last an hour or more and distance is minimal protection. Evidence: detailed analysis of restaurant transmission, where adjacent tables as well as tables 20+ feet away connected by air flow patterns were the ones affected. Distance is the next most important factor. Mask wearing has to be near universal because the weaknesses of non ND95 masks are minimized if all parties wear them (at least covering nose and mouth).*

That's the only case so far - is it a special case? Restaurants have opened in Singapore with safe distancing for quite some time now, with so far no rise in the rate of infections. People are unmasked while eating.

Incidentally, the authors of the report about the restaurant transmission case are cautious about inferring aerosol transmission. I do agree this one case is the strongest evidence to date for the possibility of aerosol transmission.

https://wwwnc.cdc.gov/eid/article/26/7/20-0764_article
"Virus transmission in this outbreak cannot be explained by droplet transmission alone. Larger respiratory droplets (>5 μm) remain in the air for only a short time and travel only short distances, generally <1 m (2,3). The distances between patient A1 and persons at other tables, especially those at table C, were all >1 m. However, strong airflow from the air conditioner could have propagated droplets from table C to table A, then to table B, and then back to table C (Figure).

Virus-laden small (<5 μm) aerosolized droplets can remain in the air and travel long distances, >1 m (4). Potential aerosol transmission of severe acute respiratory syndrome and Middle East respiratory syndrome viruses has been reported (5,6). However, none of the staff or other diners in restaurant X were infected. Moreover, the smear samples from the air conditioner were all nucleotide negative. This finding is less consistent with aerosol transmission. However, aerosols would tend to follow the airflow, and the lower concentrations of aerosols at greater distances might have been insufficient to cause infection in other parts of the restaurant."

 

[atyy]

On the other hand, I am highly skeptical of surface transmission. Someone sneezes near a surface and it gets contaminated. Virus starts degrading at a steady rate. Someone touches the surface getting, say, 1/10 the viral load in the air near the surface at the time of the sneeze. Then, they scratch the outside of their nose, inhaling at the same time, say another tenfold reduction in viral load. Thus, compared to inhalation of aerosols near where someone recently sneezed, you have 100 fold reduction in viral load for the multistep touch transmission. Note, no amount of viral load on your hands will matter unless you touch your nose or mouth (possibly, but unverified, eyes) before washing your hands or waiting for the virus to degrade. Epidemiologists have so far documented no case whatsoever of coronovirus transmission primarily by surface touching. And of spread by droplet/aerosol inhalation, indoor cases outnumber outdoors by 50-1.

I tend to agree. But there is one bizarre case that is hard to explain. Two people attended the same church at totally different times (when I've heard the data presented in a seminar, it seems that security camera footage supports that the two people did not meet), but sat in the same seat. It has been suggested that the first person infected the second. Look at the description of "Cluster A" in https://www.cdc.gov/mmwr/volumes/69/wr/mm6914e1.htm.

 

[atyy]

However, epidemiologists are now more and more agreeing with the idea that for indoors protection when others are not wearing masks, the only adequate protection is an ND95 mask, irrespective of distance

This paper supports that the restaurant case you mentioned was likely due to aerosol transmission. However, it does not support what you say about "irrespective of distance".

https://www.medrxiv.org/content/10.1101/2020.04.16.20067728v1
"However, the formation of a contaminated recirculation envelope in the ABC zone cannot alone explain the outbreak. Further evidence comes from the low ventilation rates: the observed high concentrations of the simulated contamination result from the lack of outdoor air supply. The exhaust fans in the walls were found to be turned off and sealed during the January 24 lunch ... The measured average air flows of 1.04 L/s and 0.75 L/s per patron in the non-ABC and ABC zones, respectively, are considerably lower than the 8–10 L/s per person required by most authorities or professional societies"

"It is important to note that our results do not show that long-range aerosol transmission of SARS-CoV-2 can occur in any indoor space, but that transmission may occur in a crowded and poorly ventilated space."

"The average room concentration of aerosols is thus a function of source strength and ventilation rate. When the ventilation rate of the room is sufficiently low, the room average condition can become as concentrated as within the exhaled air. Hence, in theory, even if an infectious agent is not typically (i.e., under adequate ventilation) transmitted by a long-range aerosol mechanism, the spatial extent of transmission increases if the ventilation rate is very low. We refer to such transmission as an extended short-range aerosol mechanism."

 

[.Scott]

I tend to agree. But there is one bizarre case that is hard to explain. Two people attended the same church at totally different times (when I've heard the data presented in a seminar, it seems that security camera footage supports that the two people did not meet), but sat in the same seat. It has been suggested that the first person infected the second. Look at the description of "Cluster A" in https://www.cdc.gov/mmwr/volumes/69/wr/mm6914e1.htm.

There is no reason that you need to be in the same room at the same time to become exposed to a SARS-Cov-2 aerosol. The particles are smaller than tobacco smoke and will remain in undisturbed air for hours. If there is pedestrian traffic, it will not settle out. The limiting factor becomes the survival of the virus in that environment - which is related to temperature, humidity, and sunlight.