It’s not a mere semantic debate - if I understand correctly (not a virologist or anything) the implications are huge.
Droplets are ejected from the face and basically fall straight to the ground. This is what makes things like six feet “socially distancing” rules effective - you basically need to be in a direct, face-to-face interaction with someone to spread the virus. Airborne transmission in the technical sense means that the virus can float along in the air, potentially for hours in a poorly ventilated space: most social distancing NPIs become nearly meaningless. Staying outside or improving indoor ventilation become the big things that matter.
Also, droplets are large and are stopped effectively even by the sort of cheap, relatively loose-fitting masks people are wearing. If airborne transmission is a major problem, that’s no longer really the case; we all need N95s to make much of an impact.
That was the messaging in the first couple of months, and why social distancing was thought to be sufficient: The droplets would fall to the ground before traveling very far.
Then several months later we started hearing about how the virus can hang in the air for hours in buildings with poor ventilation; that's aerosols, not droplets. At that point social distancing does almost nothing, and even masks are questionable since it can far far more easily go around the edges of any masks, and slip through cloth masks in ways droplets can't.
> people can get infected further away than with larger droplets
Minor nitpick, you can think of aerosol transmission as plume of virus particles. Technically you can get infected long after the carrier has left a closed room, at which point the concept of being "further away" stops applying.
Your claims do not reflect what the article and the evidence it cites show. To quote:
> Cowling told me that it’s better to call these “short-range aerosols,” as that communicates the nature of the threat more accurately: Most of these particles are concentrated around the infected person, but, under the right circumstances, they can accumulate and get around.
This is the precise opposite of your claim that 6 foot distancing would "matter little under aerosol conditions where air flow patterns dominate transmission." AT NO POINT does the article indicate that droplets are irrelevant. We know they are the key factor in person-to-person transmission. But we also now have evidence that short-range aerosols also play a role, especially in superspreading events.
The evidence is VERY clear that risks are highest in close proximity to infected individuals.
I would encourage you to take another look at the article and read closely.
> If someone with coronavirus sneezes in a room, the large heavy droplets will quickly fall to the ground.
This is the slightly incorrect part with COVID.
Traditionally, this would be an appropriate description for other droplet transmission (like the flu). However, it seems COVID has an above average ability to survive in extremely fine droplets - think mist-sized particles that CAN float in the air for an extended period of time (given the right circumstances).
This nuance is challenging to convey. For healthcare workers, it's important because it likely means standard droplet based precautions are not enough. However, it also seems that full airborne precautions (PAPR's) are overkill. My take is N95's do enough to dehumidify droplets and ultimately break down particles.
For the general public, the nuance is less important. Most don't have access to proper fitting N95 (or better) masks, so they're stuck wearing cloth or surgical masks. They should simply think of COVID as airborne because they're likely not wearing the proper gear.
Droplet is the "popular" middle ground. Contact is completely overshadowed by both types of air travel unless air travel is either completely out of the picture (non-respiratory viruses like various herpes) or if the virus particles excel at durability outside the body (e.g. the rhinovirus family, whereas being bad at this is an outcome of the defining property of corona viruses, they are short-"lived" almost by definition).
And droplet basically translates to: "yes, masks would help, but simply keeping a few feet of distance will be just as good". Unfortunately, distance does to aerosol transmission what soda cans do to a wildfire.
”The 6' radius limit is nonsense for this disease.”
Epidemiologists do not study individual cases; they study statistics. For that, social distancing helps in the sense that it decreases the speed at which this spreads.
AFAIK, this virus needs water to survive. If so, it depends on how long droplets will survive in the air. Larger ones will fall down sooner, smaller ones will evaporate sooner (all depending on humidity and temperature)
https://www.ncbi.nlm.nih.gov/books/NBK143281/ says ”droplets >5 µm in diameter that fall rapidly to the ground under gravity, and therefore are transmitted only over a limited distance (e.g. =1 m)” and ”large droplets comprise most of the total volume of expelled respiratory droplet”
So, keeping a small distance decreases the probability of infection, but doesn’t prevent it.
Edit: figure C.2 in that article shows the “Wells evaporation-falling curve of droplets”, which shows that, at room temperature, a diameter of around 120 µm is the worst, time-wise. Smaller droplets evaporate sooner, larger ones fall down earlier (all assuming zero convection, I assume, something that isn’t realistic)
Even droplet based spread (which is not airborne) can transfer over distances on to surfaces. This is why there is advisory for a 6+ ft physical distance.
That does not mean it is an airborne disease, as it seems the virus needs to survive in droplets.
It is no surprise to me that a choir singing could easily spread droplets on to surfaces and inadvertently touch their faces during that time.
Even a heavy breath that expels air and droplets from the lung can cause spread. That doesn't mean its airborne.
The issue of an airborne disease is not just a matter of droplets, but whether infectious particles are aerosolized such that they hang in the air for hours. The 6 feet social distancing rule only makes sense in the context of droplet based, non-aerosol transmission. It was only after more than a year into the pandemic that CDC acknowledged that COVID is airborne and updated their guidance.
The title is highly editorialized misinformation. The study is saying that aerosolized virus is pretty much nonexistent outdoors (as everyone expected - fresh air works), but does not deny droplet transmission outdoors, which is what social distancing and mask wearing is designed to prevent.
From the abstract: "Transmission by contact or at close range due to large respiratory droplets is widely accepted, however, the role of airborne transmission due to small respiratory droplets emitted by infected individuals (also asymptomatic) is controversial"
The distinction here is between droplets and aerosol transmission. As I understand it, droplets are relatively large chunks of water (or whatever), and aerosols are particles in suspension in a gas. At the beginning of the pandemic, most scientific professionals assumed that COVID-19 was transmitted by droplets; the 6 foot distancing advice comes from that assumption, since droplets don't have much range.
(Which is not to say that increasing distance didn't help, but 6' wasn't a magic number.)
That agrees that the virus is mostly transmitted via droplets rather aerosolized virus particles. A bare virus can float in the air for quite a while but all the evidence we have, especially stuff like form that site, seems to show that that isn't a route by which people are being infected. Instead its being transmitted over shorter distances, generally around 6 feet but longer if someone is shouting, singing, coughing without covering, or just directly downwind.
Zeynep Tufekci published an excellent article about this. Her thesis is that medical dogma insisted COVID (and other infections) spread through droplets and not aerosols. Social distancing is enough to prevent infection from droplets because they don't travel far. That, it turns out, is wrong, and COVID can spread through smaller respiratory particles that can float, making social distancing alone ineffective.
The virus isn't truly airborne. The respiratory droplets can be carried in the air short distances, but direct infection from that is extremely unlikely outside of someone literally sneezing in your face.
This is in contrast to diseases like anthrax, where particles can be carried on air currents basically indefinitely and direct infection from the airborne disease is likely.
Your intuitions about airborne transmission are based on the idea of viruses being carried in relatively huge droplets of water, which due to their size and weight would rapidly fall to the ground. Hence constantly wiping surfaces clean, sneezing into the nook of your arm, mask mandates and lockdowns reducing transmission, etc.
This theory is inconsistent with the evidence: mask mandates have no effect on case numbers and nor did lockdowns. Whether you like this or not is irrelevant - the data is final. Therefore the droplet theory is wrong, and by extension theories based on it are also wrong.
There is an alternative theory of how SARS-CoV-2 spreads through the air: that the viruses can exist in fine aerosols that can be suspended in the air for relatively long periods. This theory is consistent with the evidence actually available:
1. It's consistent with islands that closed their borders early being able to keep the virus out, but nowhere else.
2. It's consistent with mask wearing having no effect, because masks aren't airtight. You still need to breathe in the surrounding air and the holes in masks are much too large to stop a very fine suspended aerosol. Additionally it wouldn't matter even if they are airtight and very good filters because there's evidence the virus can enter via the eyeballs too.
3. It's consistent with lockdowns having no effect. Even in "lockdown" lots of people still need to be in areas recently vacated by other people, like shops, factories, anything to do with the supply chain.
4. It's consistent with the apparent lack of infections outside. Where the wind blows, aerosols emitted by an infected person are rapidly dispersed in the air.
5. It's consistent with the failure of measures like handwashing to keep the virus out of care homes.
It's also consistent with SARS-CoV-1, in which an outbreak was investigated and the conclusion was it circulated through an apartment block via air in drainpipes:
That isn't possible with the droplet theory, but is perfectly possible with aerosol theory.
The fact that "actual scientists" doing "real research" show that masks work is actually evidence that their research is garbage and they aren't "actual scientists", at least not if we define scientists as people who successfully apply the scientific method to understand reality. If they worked then you'd be able to consistently see the impact in case numbers, but that's simply impossible.
If you read any of their studies you'll soon be struck by how universally poor the quality of COVID research actually is. The scientific method as normally meant has more or less gone AWOL and what's left behind is a bunch of people who very much have an agenda desperately trying to justify why their previous advice wasn't wrong. I really couldn't care less what "actual scientists" think at this point. If they want to be taken seriously they need to provide evidence that's strongly convincing on its own merits, because their institutional credibility has long since turned to dust.
There is a very succinct explanation by Michael Osterholm [1][2] where he says that the virus is spread both by droplets & aerosols, and that sharing the same air with another person is the primary vector (that isn't intended to sound as alarmist as it probably does).
From what I understand the best prevention is to reduce face-to-face contact with other people where possible, but an N95 mask would definitely help prevent contraction in public spaces.
Of course, these measures seem extreme since ~80% of people will barely notice they are infected / have mild symptoms, but it's all about peak-load reduction.
You are right about viral load being a factor. You are not right about only macro droplets being a problem. Micro dropplets, that are suspended in air and do not "fall to the ground" soon carry enough of the virus to be infectious in accumulation. This is why indoor areas are problematic regardless of the 6 foot spacing, as the air just gets saturated over time unless you have a continual strong crossdraft.
The smoke analogy is not perfect, as it's composition is less moist, but it is closer to the truth than the '6 foot' model that was itself already a compromise between the now accepted as disproved macro fluid projectile model and economic concerns.
Droplets are ejected from the face and basically fall straight to the ground. This is what makes things like six feet “socially distancing” rules effective - you basically need to be in a direct, face-to-face interaction with someone to spread the virus. Airborne transmission in the technical sense means that the virus can float along in the air, potentially for hours in a poorly ventilated space: most social distancing NPIs become nearly meaningless. Staying outside or improving indoor ventilation become the big things that matter.
Also, droplets are large and are stopped effectively even by the sort of cheap, relatively loose-fitting masks people are wearing. If airborne transmission is a major problem, that’s no longer really the case; we all need N95s to make much of an impact.
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