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6ft Is Not Always Enough: How Saliva Droplets Spread Through the Air (ieee.org)
27 points by samizdis 13 days ago | hide | past | web | favorite | 26 comments





Are they calculating how much the droplets travel, or how much viral load someone gets at a specific distance?

This sounds confusing. If I remember correctly, R0 for the virus was around 3 before it was controlled. Is it really plausible that a virus that can spread through droplets due to asymptomatic people breathing in the street, where those droplets travel 6m, would have an R0 as low as 3? Wouldn't it just infect everybody immediately? What am I missing?


> What am I missing?

Probabilities?

I'm sure it's possible that someone asymptomatic breathing while walking down the sidewalk infects a bunch of people. That doesn't mean it isn't also rare and maybe not a significant factor in the overall picture of the virus.

There are likely 10s of millions of people with the virus at this point. There are probably a few cases out there where they caught it through their bedroom window from someone asymptomatic wearing a mask on a sidewalk 4 floors below. That doesn't mean masks are pointless or that asymptomatic people spread the virus just as easily as symptomatic people or that everyone needs to shut their windows.


Based on those parameters, I would agree with you. I am wondering if the R0 was really as low as 3 prior to the virus being controlled, though. Any R0 measurement will depend upon the number of cases, which has always been fairly unknown with covid due to the asymptomatic cases.

I think there's also a tendency to think about R0 as something that applies in any environment, but this won't be true. It will vary a lot based on air flow, indoors/outdoors, etc. As a result of this, you'll have instances where one carrier infected 10 or more people due to being in close proximity with unfavourable air flow, even if the average carrier only infects around 3 - 5 or thereabouts.

I always think about smokers for this type of thing. The particles are probably quite different (I hope droplets don't carry quite as well as smoke!) and so perhaps there is an adjustment that needs to be made, but in certain environments you will see & smell the smoke from a smoker a lot more than other environments. This will also depend on your proximity and airflow.


The confusing issue here is the dispersion factor: the variability between infectiousness of carriers, which appears to be quite high in the case of covid-19:

https://www.sciencemag.org/news/2020/05/why-do-some-covid-19...


People who have a significant risk of death don’t care about R factor, they just want to avoid infection.

Reasonable precautions for the vast majority of people don’t seem like enough if you’re 70+.


Who are these people at risk exactly? I think there isn't enough talk about it. There are studies now that show that zero carb and intermittent fasting can reverse type 2 diabetes. But nobody seams to suggest to people at risk to try to eat less sugar.

I'm pretty sure the first thing people are told after being diagnosed with type 2 diabetes is to control their carb intake.

I actually don't think that's true. But that might depend on the country, doctors etc. Many still give the exact wrong advice of limiting fat intake, focusing on "slow burning carbs" and all that.

I tell my I’ll and overweight friends this whenever they complain of their illness. It makes me unpopular but I feel like I am not a true friend unless I speak up.

What is your point? That we should spread inaccurate information because there are immunocompromised people?

What inaccuracies are you referring to?

It’s known that people have gotten infected while standing much further than 6 feet apart. If your at 20+ times the risk of death than the general population and retired then long term self quarantine is a serious consideration. That represents a significant quality of life cost, but I would hardly call such people paranoid.


EDIT: The comment I'm replying to was edited after my comment and the "Reasonable precautions for the vast majority of people don’t seem like enough if you’re 70+." added.

Of course 6 feet isn’t always enough, they need a reasonable guideline that’s also easy to implement. Most Americans have an intuitive grasp of what 6 feet is, as the height of a “regular tall guy” and can thus estimate 6 feet much better than 8.

Europe is going with 2m, while a bit longer than 6ft, I doubt it will make much of a difference, especially in an informal setting.

I think every country in Europe is picking its own rules. Belgium, Germany and the Netherlands use 1½m, for example, as does Australia (not in the EU, just mentioning it), and France and Austria say “at least one meter”.

we are only going with 2m cause its a round number almost the same 6ft

Yes, I know, I was just pointing out the distance is slightly bigger


Also...

"Masks Don't Work: A review of science relevant to COVID-19 social policy"

https://www.researchgate.net/publication/340570735_Masks_Don...


Not peer reviewed and reads extremely politically charged. I'd hardly call this science.

Agreed. Also, if respirators don't work, how come there isn't a mass infection among doctors treating COVID-19 patients worldwide?

This doesn't even look like a "pre-print", it's worse than that. Also the text is written more like an angry internet comment than a proper academic text.

In his "review of the medical literature" none of the articles talks specifically about the Coronavirus, instead talks about the Influenza virus. They have very different sizes.



I checked the first link, it’s about the common cold. They test groups with and without masks and in both groups there was one person getting ill. Conclusion: the sample size is far too small to reach any conclusion.

Also checked the second link, it says:

There is some evidence to support the wearing of masks or respirators during illness to protect others, and public health emphasis on mask wearing during illness may help to reduce influenza virus transmission.

Not very convincingly concludes the opposite of the claim.


Of course they 'work'

Covid is spread mainly by respiratory droplets, masks act to catch those droplets at source, it's simple logic.

Whilst only a properly fitted P3/N99 mask gives absolute protection from infection via inhalation, community mask use is an important pandemic control measure to keep the reproduction rate 'r0' to a minimum.

That the advice from WHO and some governments has been muddled, illogical and inconsistent does not detract from the truth.


Which one of these have specifically studied the efficacy of masks against the Coronavirus (50–200 nanometres)?



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