Airborne viruses have been known for a long, long time. The physics is established. The whole reason we distinguish between airborne and non-airborne viruses is exactly because virus needs special arrangements to be able to survive outside of fluid.
While it is interesting how particles move in a room, it is completely different topic. The particles ARE NOT AEROSOL. The kind of aerosol that can flow in tiny air currents dries out in seconds and becomes small particles (not droplets) of "relatively dry" matter that is fine enough to stay in air for a very long time.
You claim "If the virus were truly airborne, which it isn't" yet provide no evidence.
But looking at you history you have provided exactly evidence that it is airborne "Video showing microdroplets suspending in air (vimeo.com)" a few months ago (https://news.ycombinator.com/item?id=22776194)
And to quote from another commenter "The part showing how a single cough can create a room-wide cloud of virus that lingers for 20+ minutes in spaces with poor circulation was especially enlightening."
Having watched the vid I can confirm that's what they show, at least as a simulation.
Even the main article says (I'm re-quoting from another of my posts): "There is a big dispute in the scientific community, however, about both the size and the behavior of these particles, and the resolution of that question would change many recommendations about staying safe. Many scientists believe that the virus is emitted from our mouths also in much smaller particles, which are infectious but also tiny enough that they can remain suspended in the air, float around, be pushed by air currents, and accumulate in enclosed spaces" which directly opposes what you say.
How is your parent post not either plain wrong or deliberately sowing confusion? I'm flagging you.
Yes, it is, but IIRC the term "airborne" can also refer to disease particles that can survive in the air unencapsulated (such as certain fungi), and can therefore travel quite some distance, and can remain hanging in the air for hours.
Aerosols are heavier than air, and therefore have a very limited range and duration in which the virus can remain "airborne" in common parlance.
(edit: expanded the definition to include more than just viruses as I couldn't find an example of a virus that can survive unencapsulated)
As far as I understand it lives in droplets heavier than air that fall to the ground in a matter of a few seconds. The next person entering the elevator won't breathe it. Truly airborne viruses can be lifted by regular air turbulences and travel kilometers before landing on someone else.
The idea of respiratory viruses not being airborne sounds silly. What's the viral charge supposed to do, not jump into droplets smaller than certain size?
Of course they are present in the smallest droplets! They are present in the mucous secretions of the infected individual and they will get expelled through the big and the small droplets.
The distinction shouldn't be a qualitative one, airborne vs not airborne. It's a quantitative one, sufficiently infectious viruses may pose a risk at much smaller doses, the kind that you may be exposed by the smallest droplets expelled that simply stay afloat.
It's also worth noting that human immune response is a complicated beast, what may not be infectious for an average healthy individual may put down someone with a weakened immune response. So even supposedly "not airborne" viruses that are very unlikely to infect the average healthy individual at very small doses may pose an "airborne" risk for individuals with a weakened immune response.
There are more factors in all of this, atmospheric conditions may play a role. For example, cold temperatures may be more suitable for the virus to remain infectious outside of a host, thus increasing the likelihood of "airborne" propagation.
TL;DR: The distinction between airborne and not airborne viruses is an artificial one. That only makes sense statistically for an average individual at certain atmospheric conditions for a concrete strain of the virus. But as any real-world statistical distribution there are tails and you will find "airborne" qualities for pretty much any respiratory virus in those tails.
There are two types of viruses: airborne and not airborne. Airborne can survive for some time outside bodily fluids.
Aerosol == bodily fluid that is still liquid. It is just in the form of very small droplets that are now drying out. Depending on conditions this lasts very shortly. It spreads the virus, of course, but aerosol dries out quickly and viruses that are not airborne die (well.. viruses do not live in the usual sense, basically their proteins get damaged).
Of course if somebody coughs in your direction some of the aerosol can be inhaled or reach your retina or get on your hands and you can get infected.
No, I am not suggesting droplets cannot spread the disease, the opposite is true. Droplets are much better transmitter of disease if they can reach the target.
No, the WHO was right, and still is, epidemiologically speaking. The problem is that there is a difference in meaning between "this virus is airborne" and "this virus can spread through the air via aerosols".
The former means that the virus itself can survive being exposed to the air, which means it can float for hours and spread easily over large distances.
The latter means that the virus can only survive in the air when encapsulated in a liquid, which means it can not hover in the air for long (due to the weight of the droplet) and thus not spead over large distances.
I thought that "airborne" meant "could survive in water aerosols for long enough to get breathed in" not "sprouted little virus wings and flew through any hole it could fit through"
And I assumed water droplets were in fact several orders of magnitude larger than the virus, but would still be caught my masks. Otherwise what's the point for any virus?
Your observations are correct, but your implied conclusion is not.
In the 'real' environment micro-droplets are shown to be suspended for minutes. It is the larger droplets that are pulled down by gravity and do not make it far. But the micro droplets can contain more than enough virus particles.
It is shown that the room gradually accumulates more and more suspended droplets as people continuously produce them, not just through sneezing and coughing, but just by talking and breathing.
In a typical office environment there is continuous low velocity air circulation spreading these droplets through the room and saturating the whole space with them.
The video shows also that cross drafts, which produce a high air replacement, can take the droplets outside of the room which is a good thing. The moment the draft is closed the accumulation starts anew.
The same article then also goes on to reason why this doesn't seem to be the dominant way of transmission outside special circumstances (like ventilation).
I don't have a background in this topic at all, but apparently actual airborne viruses are really small: Measles is about 200 nm and Influenza about 100 nm in diameter, while Sars-Cov-2 is about 1000 nm, so 5 to 10 times the diameter and thus 100 to 1000 times the mass.
> Until 2020, healthcare authorities in the Western world were were certain that viruses could never remain airborne for extended periods of time.
There was certainly mainstream belief that covid was limited to droplet transmission (though I remember much discussion of that as well) but the idea that Western medicine didn't think any viruses were airborne is nonsense.
Another comment brought up measles, which is a great example, and known for many decades.
While it is interesting how particles move in a room, it is completely different topic. The particles ARE NOT AEROSOL. The kind of aerosol that can flow in tiny air currents dries out in seconds and becomes small particles (not droplets) of "relatively dry" matter that is fine enough to stay in air for a very long time.
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