Hacker News Reader

Comment by jennyyang | Hacker News Reader

They have discussed this ad nauseum. It's not airborne. It's designated as "airborne droplet".

I read an article from a epidemilogist that wrote about a very recent study of an isolation chamber for a covid-19 patient. They detected the virus everywhere on surfaces in the isolation chamber. This is consistent with airborne droplet spreading, since the patient was presumably coughing and droplets were being spread throughout the isolation chamber.

What they DIE NOT find was the virus in the air. If it's truly airborne like measles, it would be detected in the air itself, but that was not true. Thus, it is not airborne.

I don't have the source for this, because I probably read 200 articles a day like everyone else so it's lost in my history. But I actively committed this to memory and reassured me that this was not airborne, but rather airborne droplet.

View on HN

This is an important distinction for experts who know the terms of art, but for regular people it is maybe misleading to keep insisting that "it isn't airborne".

It is traveling through the air, you can get it, through the air, if you are near another person.

I have seen this misunderstanding in real life. People who think an outdoor festival is safe because "it isn't airborne"

As well, at least one expert, in South Korea, states that it is possible to become aerosolized and actually airborne in the right conditions (many people, singing, shouting, in a small area). Source: https://www.youtube.com/watch?v=gAk7aX5hksU&t=1559s

When you tell people who have zero experience or understanding with/of this sort of thing, you end up accidentally convincing them they can only get it through direct contact with an infected person. Without the additional context it also conflicts with the explicit guidance for staying at least 1m away from people.

The “explicit guidance” is also minimally scientific: it varies from 1m in (parts of) Europe, to six feet in the US. These things are being made up on the fly.

There is no solid science for how far apart people should be, and there are so many complicating factors (what kind of room? how much airflow?) that any such guidance is a rough guideline, at best. Folks who are stringently trying to stay six feet apart from each other while walking down the street in Manhattan, for example, are more than a bit silly.

The GP is a reasonable statement of the current scientific knowledge: it isn’t airborne, and you actually do need fairly intimate contact to get the virus “through the air”. Spending hours together in an unventilated room is probably sufficient, even if you never get closer than 1m; conversely, it probably doesn’t matter much if you pass right next to someone on the street(unless they cough directly in your face).

FWIW, the YT video you recommend has a lot of interesting info from the person who’s reportedly Korea’s foremost expert. Among other things, he mentions cases of reinfections.

The reinfection debate has been murky. Is it just a testing artifact, etc? Notably, he did not mention any of these alternate explanations. He stated rather plainly that they have seen cases of reinfection.

This was one of the things that came up in the meta-discussion last week.

HN loves to make "well ackchuyally" posts that are technically correct but meaningless to the layman. It's a result of the "points scoring" format of the site, same as Reddit. It leads to people having to make cumbersome posts that fully specify every single point that might possibly be the subject of any disagreement, and that's antithetical to good, informative, concise content.

Pedanticism is not the same thing as content. In fact, it usually crosses the rules of the site into "not giving the most gracious possible reading of a comment". And yes, you have to strike some balance between being pedantic and being accurate.

To the layman, if you don't already understand the difference between aerosol and airbone transmission, there really isn't one in practice. Being around an infected person can cause you to become infected yourself, without direct physical c. That is the short and long of it. It doesn't shed off their skin, just when they breathe, or talk, or sneeze, or cough, and potentially can linger for hours. There is no meaningful difference in how you would behave if this was airborne vs aerosol.

Everyone thinks their particular "well ackchuyally" is important, but usually... they're not.

The intentional misspelling comes off as mocking and derisive, which risks undermining the point.

But to that point... I'll admit I have been there. At times, if I'm just relaxing, constant corrections can feel pedantic, endless, tiring, and uncharitable.

I see the other side too though. Other times, I really need a place for careful discussion of ideas, where we all try to contribute what we know and learn from each other, as a refuge from all the places dominated by anti-intellectualism.

So I know it can be draining, but I'd hate for peer pressure from a vocal minority to chill useful intelligent contributions in other threads. I don't want anyone to feel like they'll be made fun of for simply trying to contribute to a discussion.

Unimportant "well actually" posts can be downvoted or ignored. There's no equivalent workaround for overcorrection, no way to save the insightful addition someone never posts to avoid the risk of getting made fun of.

I think this is very wrong. Looking back I think this distinction is what people will point to as the big mistake people made. This idea of large droplets in itself is basically meaningless. I encourage everyone to read [O] very carefully. This thing will shed into the air, and it will infect others. Countries that encourage everyone to wear masks will succeed in containing this. There is way too much bs being discussed around large droplets. The paper I link to is looking at influenza A in particular, but I am making the very strong assertion that SARS-CoV-2 will show significant homology with regard to transmission behavior. I think the rates of infection alone bear this out if people think clearly about this.

[O] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2843947/

Yes, this article points out that aerosols are much smaller than droplets and that health officials see this event as evidence of the aerosolization of the coronavirus. The aerosolized virus may even stay in the air for 30 minutes.

It seems we all should be wearing masks in public!

>Countries that encourage everyone to wear masks will succeed in containing this.

Isn't the main reason for the success of this measure precisely to make any infected people retain droplets (big or small) inside the mask?

I'm not saying it doesn't offer any protection from droplets in the air, but the main motivation was containing droplets.

In this case, Choir practice it's literally a spit fest - you're singing loudly in a tightly packed large group of people. It's like the perfect scenario for spread.

Even if they are in rows, you get them on your head, neck, shoulders, hands, pants, sheets of paper you're holding, even shoes.

Also, if it is indeed suspended in air, then wouldn't the minimum requirement be N95 masks?

>Isn't the main reason for the success of this measure precisely to make any infected people retain droplets (big or small) inside the mask?

The one thing that people don't seem to think about is even if it's only effective at keeping droplets from infected people from spreading, how are all of the asymptomatic supposed to know they should wear a mask?

The obvious solution is that everyone should wear a mask. I think people keep discouraging mask use due to the shortage, but if people are misinforming the public due to a shortage that's still not cool

Oh most definitely - agreed 100%!

Communication wise isn't straight forward, but in this case I think the masses should know it bluntly. "You could be a source of spread, so use a mask in public."

Because on one side I understand that "use masks" might give a sense of false security, and stresses supply chains... but there are other ways of doing it - promote community production, even if it is rudimentary. Some countries are using prisons. I mean, there are ways around it.

> I think people keep discouraging mask use due to the shortage, but if people are misinforming the public due to a shortage that's still not cool

I haven't seen ant misinformation discouraging mask use.

I have seen people point out: (1) it is most critical that healthcare workers have masks, (2) masks are not particularly effective for protecting the wearer, but they are very helpful for protecting others from the wearer.

#2 is enough to discourage use from the selfish who are unconcerned with social consequences, #1 tends to discourage those who are concerned with social consequences, given the supply shortage.

But it's bullshit, because non-N95 masks are effective at protecting the wearer, about half as effective as N95 masks, and if "selfish" people wear masks to protect themselves they will also protect others from themselves. The authorities are feeding the public bullshit to protect mask supply, and the public isn't stupid enough to believe it, but social norms will have to change in the US quite a bit before wearing masks everywhere all time time (even with no pandemic, as is common in many parts of Asia) will become socially acceptable.

No--emphatically no. N95 will protect you from aerosols which is why we desperately need like a billion of them, the key point being protect you. It doesn't matter which side of a wall you are on, if it is concrete you won't be able to see the other side. It makes no difference which side of the N95 wall the virion particles are on--they won't get out or the won't get you. My take on this is that the the government knows everyone needs an N95, however there simply aren't near enough and so the obvious fact that this is a baseline requirement is being downplayed. I will say this clearly: everyone in America needs an N95 now and for the foreseeable future in public. That is the optimal way to proceed--because it is aerosolized, period end of story.

The best outcome is to have some development regarding N95 production, because it's not going to happen in the current scenario.

I'm not from America. I'm from Europe. So you're basically saying we need tens of billion of masks worldwide... that simply won't happen.

I understand that would be the optimal solution in your opinion. But some countries are showing good results with a not so optimal solution, which is surgical masks and home made masks.

In the US we are using the Defense Production Act to make ventilators--this is good, but really we need the focus to be on N95 masks. With the current level of disinformation regarding droplet spread this isn't happening--this is the tragedy. We need the leaders of the world to realize that it really is N95 masks that are going to be the key. You can safely restart more portions of the economy with everyone wearing PPE that is of high quality and effective. The fact that this isn't priority one is mind boggling.

The problem of N95 is sourcing the plastic mesh with static charge - the major filtration portion.

As odd as this my sound, but at the moment you might have a larger bottle neck in N95 production than you have on ventilators (taking into account the disposable nature of N95 masks and the sheer volume required for usage, I'm not trying to compare ventilators to N95 in terms of complexity or their production lines).

Of all of this, I think an effective treatment seems to be the fastest solution (though there's none available yet), where you'd deploy treatment only to those in intensive care and ICU.

N95 masks are just too damn uncomfortable when worn properly to become the default standard at all times. Surgical masks should be the all-the-time standard with N95 for the vulnerable or anxious. It would be great if being seen in public coughing without a surgical mask on (or even being without a mask on) becomes stigmatized.

Medical professionals consider transmission through the air by small droplets like this to be 'Airborn Transmission'. See the page on the Johns Hopkins site[0], and the Wikipedia page on Airborn Diseases[1].

The difference between 'droplet' transmission such as flu and the 'airborn route' is just the size of the droplets. Infections flu droplets need to be so big they don't linger in the air very long. They tend to be projected ballistically and mainly end up on surfaces and spread by contact, while the smaller droplets such as the ones that seem to spread Covid-19 linger in the air and can be conducted via air flows such as ventilation systems.

Measles, which you cite as truly airborn, is also spread by small droplets and would almost certainly be captured by the 0.3 micron filters described in the study you seem to be referring to [2] that were used to scrub the air samples, the same fineness as N95 masks recommended for protection agains Measles.

[0] https://www.hopkinsmedicine.org/health/conditions-and-diseas...

[1] https://en.wikipedia.org/wiki/Airborne_disease

[2] https://jamanetwork.com/journals/jama/fullarticle/2762692

It's unfortunate that you don't have the source, because it would be nice to see how long after after the covid-19 patient left the chamber they tested the air for the virus.

People need to understand that there is a good possibility that this virus can stay in the air, even if it is only for 5 or 10 minutes. If using the word airborne isn't correct use of scientific jargon, it at least is correct use of common English.

The article mentions another test that measured three hours in the air, though they say it's probably no more than half an hour in real-world conditions.

That’s a lab test where they first aerosolize the virus and then spray it into the air and measure how long it lasts.

It doesn’t necessarily reflect what actually happens when someone breathes or coughs.

Yes, the researchers thought that in normal instances that it could last 30 minutes in the air. Also, health officials are pointing to instances like this choir practice to show that aerosolization of the virus is an important thing to take into consideration.

If it's the same test I saw, it was at least 3 hours in the air; they stopped sampling at that point, as they were mostly measuring different surface persistence.

Half an hour is an eternity in an elevator though

I'm pretty sure this is the study you are referencing: https://jamanetwork.com/journals/jama/fullarticle/2762692

The thing is, though, Covid-19 doesn't cause coughing in asymptomatic cases.

I had no cough before developing fever and muscle pains, and only a very mild cough afterwards. Are you suggesting that asymptomatic cases are not infectious?

Likewise, according to the article, "nobody there was coughing or sneezing".

You ever breathe out on a cold winter day? Your breath is humid.

Exactly! But I wouldn't describe this humidity as "droplets", like you would produce from coughing or sneezing.

I might not describe it that way either, but do medical professionals describe it that way?

It's not just large droplets that seem to carry the virus but also aerosolized droplets that travel farther when you cough or sneeze and that are emitted from talking and singing.

Yes, exactly my point.

Talking and singing produce respiratory droplets and aerosols. See https://www.lesswrong.com/posts/Jnq2A7A7ytgttQ5Ek/covid-tran... and the references cited therein.

> They have discussed this ad nauseum. It's not airborne. It's designated as "airborne droplet".

The case at issue here strongly suggests aerosol, not droplet, transmission; that's the whole point. Aerosol transmission is smaller particles that remain suspended longer than what is classes as droplet transmission, and droplet precautions aren't adequate for it. It's a bit fuzzy whether it is necessarily actually classed as airborne transmission but of defined precaution classes it requires airborne rather than droplet precautions.

Yes, the COVID-19 is mostly being treated as only having droplet transmission (and therefor requiring droplet and not airborne precautions), which is potentially a major error if it can be transmitted on aerosols.

The term for the sliding scale between airborne and contact only spread is aerosolized.

It's still a not universally agreed to term or concept, but likely will be, especially after this ordeal.

Not everyone agrees with this assessment. https://www.nejm.org/doi/full/10.1056/NEJMc2004973

oh I get it, the virus teleports from the patient to the surface, no air transmission. /s

(you're splitting hairs, and the implied medical advice will actually kill people who follow it - much MUCH MUCH safer to simply say "airborne" to the general public, who need a simpler model than this)

The distinction you are making is one of radius of distribution.

Someone infected with measles shedding the virus can send it far and wide...

COVID-19 needs a carrier, a bit of water/mucus to survive in. The radius of distribution is smaller (6 feet) but these drops can linger in the air depending on ambient conditions.

EVERYONE needs to put on a mask, not to avoid catching it, but to avoid spreading it... The fact that our national policy doesn't reflect this is negligent, and in the end it will have caused unneeded deaths.

https://www.sciencemag.org/news/2020/03/not-wearing-masks-pr...

https://www.sciencemag.org/news/2020/03/would-everyone-weari...

https://www.medscape.com/viewarticle/927723

https://www.fda.gov/media/136449/download

The real question is how long can it linger in the air? Seconds, minutes, hours? There seems to be a lot of social pressure to stay indoors, and that social distancing with a 6 foot radius isn't good enough.

> The real question is how long can it linger in the air?

There is an article out there that outlines this for other airborne diseases but I can't find it... Hot and dry is going to be the outright winner here...

Here is a case where it traveled 4.5m and lingered for 30 minutes: https://www.scmp.com/news/china/science/article/3074351/coro...

This was an interesting article. Thanks for posting.

> The radius of distribution is smaller (6 feet)

The article says that 45 people out of a group of 60, in a large room with chairs spaces at least a foot apart and twice as many chairs as people, all became infected without any physical contact.

The 6' radius limit is nonsense for this disease.

”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)

The studies of droplet dispersal are laboratory, not field studies. And they are imperfect models of how the virus is transmitted in the actual field.

We are being given many many natural experiments. Posts like the parent here, claiming to refute and invalidate actual experience will have to eventually acknowledge reality.

Otherwise it's "who are you going to believe, me or your lying eyes" retreat to authority.

Reply on news.ycombinator.com