Failure to recognize when an aerosol isn't a droplet, but without the stubborn dissagreements. 7

[moon161]

For discussion of the primary matter of this thread, but the stubborn dissagreements can remain there.

https://www.eng-tips.com/viewthread.cfm?qid=483537

 

[Fischstabchen]

TugboatENG,

You aren't trying to catch the virus but whatever the virus is attached to. In addition, the severity of the illness appears like a lot of viruses to be dose dependent. A lot of these medical personal who died I believe did because their initially exposure was so severe. People used to inoculate people with small pox by having them sniff ground up scabs from someone with small pox up their nose or run a single thread with blood from someone with small pox through an open wound. Of course, sometimes people still developed full blown small pox but it was at a much lower rate. I suspect that mask, even if not 100% effect, might be providing a similar effect or in the least reducing the severity of the illness.

 

[IRstuff]

The continued argument about masks not protecting the wearer simply flies in the face of logic and common sense. Regardless of the what the actual efficacy is, under any given circumstance,, be it 50% or 90%, it's better than breathing raw air, period.

https://www.preprints.org/manuscript/202007.0613/v1

https://ncceh.ca/documents/evidence-review/basics-sars-cov-2-transmission

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[TugboatEng]

"An accurate quantitative estimate of the infective dose of SARS-CoV-2 in humans is not currently feasible and needs further research. Further work is also required on the relationship between routes of transmission, infective dose, and outcomes."

This is where we are at. We simply don't know. It's reasonable to question any assumptions at this point.

 

[Fischstabchen]

TugboatENG,

You could say the same about near anything and the pandemic would come and go before the science has come to a firm 100% conclusion. There is evidence that shows a correlation between dosage and severity and this is common among many viruses. I don't know of what evidence there is that counters this even if it is presently just a hypothesis.

I get tired of this continual rant about what the science has confirmed and what is unknown. If I was working with some chemicals that had unknown carcinogenic effects but there was lot of evidence that suggested it was carcinogenic, I would suit up with proper PPE regardless of what has been confirmed. This pandemic has literally fleshed out those who would just keep doing as is instead of prepping for what could be. It is like keeping on driving while their car makes loud funny noises because it could be something minor instead of bringing the car in to a shop. It is the anti-thesis of precaution and safety and in a forum full of Professional Engineers, whose duty is to protect the safety of the public, it is a little unexpected.

 

[Alistair_Heaton]

Truth be told most of the protocols are actually naval 1700 quarantine requirements.

 

[electricpete]

This is where we are at. We simply don't know.

#1 - So are you now saying you simply didn't know when you said "That's why I think masks that are anything but 100% effective are useless for preventing infections. " (?)

#2 - Referring to the model I provided above, we do have the ability to draw some conclusions about where our interactions might lie on the curve, even without rigorous infectious dose estimates. We can simply note that we have had many encounters and yet (for most of us) we never got covid (as verified by any testing that we've had done). If we had even one interaction a day during the first year, then that's 365 interactions, and if none of those interactions resulted in infection then it's a darned good bet those encounters were on the left side of the curve (near proportional reduction in risk with filtering efficiency) rather than the right/flat side of the curve where infection is near certain.

I'm fully on-board with saying we should all be humble about how well we understand this thing. It applies to the scientists and it applies doubly to us laymen. I wish you would move in that direction.

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(2B)+(2B)' ?

 

[IRstuff]

That rule doesn't apply to trolls.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[TugboatEng]

It's hard to say we had many encounters. Even at the peak case load the number of identified cases was still less than 1 in 1000 of population in the USA.

 

[electricpete]

It's a good clarification, not every trip out of the house brings you in direct contact with an infected person.

But a lot of the time (grocery store, at work, etc), there is not just one person in the space but a large number of people in the space. And you are not only faced with the people that are in the space at the same time as you, but also the people who may have been there in the last hour or two (potential settling time for aerosols).

And each person is infectious not only for one day (in which case infectious fraction would be same as case number fraction) but likely for 2 or 3 days and as much as a week.

With all that said, not all people are the same. Some people at certain points in time are identified as superspreaders much more infectious than average. Certainly if you spent several quality hours getting cozy with one of those superspreaders in their prime spreading window, then I'd agree you're probably on the right side of the curve where the 50% mask would probably not have very much effect on an almost-inevitable infection. On the other hand, if you happen to walk briskly past that same superspreader at a distance of a few feet, then I'd think you'd definitely want to have that mask on for the best odds.


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(2B)+(2B)' ?

 

[Alistair_Heaton]

it was way higher than that in some places Tug... one state up north had 3500 in 100 000 at one point. Which did make me wonder why they were bothering with vaccination within 12 weeks they would have hit 75% anyway.

I think the super spreader having a mask on would have more effect than you wearing one.

 

[RedSnake]

I am not sure what exactly is the definition of a so called super spreaders?

In Sweden I seem to remember that it was used about a man that had infected many.
But this was at a large birthday party.
So if there was a lot of mingling and hugs during several hours, of course many would be infected.
It's not the same as if someone actually spreads more viruses with one breath when breathing then others.

The size of the virus is diameter 0,05 to 0,14 microns and it can vary in length with +0,009 to 0,012 microns (I think they mean the spikes here, it was called the tumors).

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein

 

[electricpete]

"superspreader" can apply to an event, or to an individual, and also to an individual at a specific point in time when his virus shedding peaks

https://www.laboratoryequipment.com/573221-The-3-Factors-That-Make-Someone-a-COVID-19-Superspreader/

According to the study results, published in PNAS, 50% of individuals with less than 650 BMI-years exhaled “significantly less aerosol” than the half of the group with more than 650 BMI-years. Essentially, the elderly, the obese and the obese elderly are at a heightened risk of transmission. Conversely, study participants younger than 26 and those under 22 BMI were all found to be low spreaders.

Within the high-producing group (> 156 particles/L), 18% of individuals accounted for 80% of the exhaled particles. The distribution follows the 20/80 rule seen in other infectious disease epidemics, meaning 20% of infected individuals are responsible for 80% of transmissions.

I'm waaay more than 650 "bmi-years". Good thing I'm vaxxed.

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(2B)+(2B)' ?

 

[TugboatEng]

That's good info Pete. It highlights California's diversion from science as they keep schools closed.

 

[Fischstabchen]

TugboatEng,

The U.S. has been way over 1 positive case per 1000 people. After it burned through NYC, immunological studies were putting the percentage infected at around 15%. 1 out of 1000 people in the U.S. is about 330,000 people and NYC had more than that by itself. Maybe, you are going by some positive test survey but immunological ,which check for anti-bodies, paint a much starker picture. If I were to guess based on the number of people I know that tested positive, I would say that about 20% of the population has had it. If you agree that the death rate is around 1%, we are at 600,000-700,000 officially dead from COVID-10 so you are looking at around 20% by that number.

 

[electricpete]

In TugBoat's defense, his comment was reply to mine in the context of how many times would a mask be challenged to defend you from coronavirus. So the relevant number for that particular comparison would not be cuumulative cases as a fraction of the population, but infectious cases at a particular point in time as a fraction of the population. Given 2-3 day infectious window, I'd think that would be around 2-3 times the daily cases new expressed as fraction of the population.

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(2B)+(2B)' ?

 

[TugboatEng]

I was commenting on the number of active cases, not the total. What is the likelyhood of coming into contact with an infected person in a day?

 

[Fischstabchen]

Tugboat,

Active cases have been way more than 300,000 or 1 out of 1000. If you buy that 20% of the population has been infected, you are looking at over 60 million people in the U.S.. We are bout a year into this but 60,000,000 / 60 weeks puts you at 1 million a week if it was evenly spread, which it wasn't.

 

[FacEngrPE]

Masks
Almost any kind of mask - except the ones with exhale valves were found in practice to be good at preventing infected persons from transmitting to others.

https://www.acgih.org/covid-19-fact-sheet-worker-resp/[/URL]][ul]
[li]With a cloth face covering (Cloth FC)…75% inward leakage and outward leakage.[/li]
[li]With a surgical mask… has 50% inward leakage and outward leakage[/li]
[li]With an N95 filtering facepiece respirator (FFR) 10% inward leakage and outward leakage. If fit tested to individual persons can approach 1%.[/li]
[/ul]

During the early part of the pandemic, my wife had the occasion to see an ER hospitalist that also worked as a virologist helping to design my employer's covid response.

N95 and P100 filters are available for these, I think he was using the P100 (99.97 percent efficient against 0.3 micron DOP.)

The point here is that high performance filters only provide high grade protection when they are not bypassing air due to poor fit. Most of us had no opportunity to fit test.

 

[waross]

Today Worldometer is reporting that 1 in 10 in the US has or has had COVID.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[TugboatEng]

With the relatively low fatality rate and high number of deaths, I'm going to have to agree with Fisch and say that the number of infected is likely closer to 1 in 5.5