How do we make this work?

psycho_dad

Well-known member
Some hurdles.

My daughter's school has decided on distance learning. No decision on sports yet. Just like here, the fate of all sports seems to rest with the fate of football. They seem to have figured out guidelines for all sports except football and the complaints were so great, that they have shelved every sport until football has a solution. Big downer is that they might require sports to cut kids to get down to a maximum number of kids. Talking 14 for CC per Gender. Not 100% decided on yet though.

Distance learning. I find it interesting that with two weeks before it begins, nearly nothing is finalized. Again, more hurdles thrown in the way than solutions. Have to have "live" classes where the teachers are at the school broadcasting out to the kids at home. Attendance will be taken, but not used for anything. Cannot record the "live" class because kids can be heard asking questions etc... so the kids can't play that back to review anything if they want. My daughter's work around is to record all her material and play that back as her live class as she sits there. She can pause it if anyone has a question and go over it, but it will still be available for kids to review whenever they want. She had thought about doing the real "live class" and having the recorded class as a reference tool, but then it's not consistent and there might not be material covered in the real live class that gets covered in the pre recorded material and if a kid doesn't review that pre recorded stuff they won't have all the material. TMI, I know, but that is the amount of thought that has to go into this. She is one of a half dozen science teachers in he school and there is no plan that all of them are going to use.

Test and quiz scores will make up 60% of the grade, but how they have been instructed to give a test or quiz gives them no way to stop everyone from just looking up the answers / cheating. They floated having the kids come to class to take the tests in person once every other week, but that was shot down.

They have had one week at school + two weeks at home plans. Half the school Mon-Tues the other half Thur-Fri. At least 6 different plans have been shot down.

It seems like the parents are making demands, and then saying you can't hold my kid accountable.

I think we have to let sports go on and be prepared to shut them down if things don't go well.

For about the 1000th time. I can't believe we are 5 months into this and don't have better solutions.

It will be interesting to see if something better comes out of this, or if it's just another lost semester.
 

GopherHole

Active member
The goal of stopping COVID-19 cases is not the appropriate goal. The goal is simply twofold, to protect the people who are going to have a serious problem or die, that’s the high-risk population, and to stop hospital overcrowding. There should never be and there is no goal to stop high school / college students from getting an infection they have no problem with. Locking down healthy people is just irrational.
 

JAVMAN83

Well-known member
fo
The goal of stopping COVID-19 cases is not the appropriate goal. The goal is simply twofold, to protect the people who are going to have a serious problem or die, that’s the high-risk population, and to stop hospital overcrowding. There should never be and there is no goal to stop high school / college students from getting an infection they have no problem with. Locking down healthy people is just irrational.
A nice, concise description of an appropriate view of logical goals.

Unfortunately, many are still under the delusion that the virus can be stopped with all the measures currently used, INCLUDING lockdowns. Got news for everyone, but lockdowns WON'T stop the virus spread...it is the air conditioning systems in millions of apartments, homes, & business that are furthering the spread. Getting outdoors is the best thing you can do! Vaccines & the development of herd immunity will mitigate the virus over time. Until that year, REASONABLE measures should be taken, but don't delude yourself or your loved ones into believing they can be 100% sure of not being exposed or prevented from dying. That is simply a fool's belief.
 

Percidae

Member
I think you will see a lot of creativity coming out of local schools as they try to reduce exposure and help everyone manage through the restrictions that will be required. It will be interesting to see what ideas will spread across the state/country.

I think that when possible, classes should find a way to be conducted outside. My wife is a language teacher at the high school level and has lots of ideas for holding class outside. This will give all of those students a break from masks which should help them keep them on when they are in classes that must be inside. If students can get outside for a class or two a day, that will help all involved.

Another idea is to do some classroom changes outside. Her school is uniquely set up for this arrangement. This eliminates congestion in halls inside and gives everyone a mask break for at least a couple of minutes. This would also require more restroom brakes during class which will also reduce congestion inside restrooms during class changes.

I am sure there are lots of other great ideas that will surface.

Some things will probably not work out but others hopefully will.

There are no silver bullets short of an effective vaccine. Just going have to do the best we can, be flexible and adapt to changes as they occur.
 

madman

Well-known member
The more reading of research I do, the more doubtful I become about holding in-person classes. A friend who is a doctor was talking to be about how useless face masks are relative to viruses, even N95 masks. I didn't believe him, so I started reading the research articles that are available online. Virus particles are on the orderof 0.1 micron in diameter. In aerosol form they are 0.5 to 2.0 micron which pass through masks and as the moisture evaporates, they become so light that they ride air currents more than fall to the ground like the droplets do. Surgical masks are much less effective than N95 masks, and cloth masks are one-third as effective as surgical masks and nearly useless against aerosols.

We are still early in the epidemic so there is still a lot of hypothesizing and not a lot of definite answers, but there seems to be a general consensus that the virus can be transmitted by touch, droplets, and aerosols; though, the efficacy of each modality isn't known.

Cloth masks do seem to reduce the distance droplets travel, but are almost completely ineffective against aerosols. As masks become damp, they become even less effective. Teachers/students working in buildings that are not air-conditioned and are prohibited against using fans (which would simply spread droplets and aerosols over a greater distance) are going to be sweating a lot. Their masks are going to get wet and even less effective.

The masks also serve as collection devices for virus particles; hence, without proper handling techniques they can serve to increase the chance of transmission by touch. Furthermore, if they are not cleaned on a regular basis this situation becomes much worse. Viruses can remain "active" for at least a couple days on most surfaces including masks.

When cloth masks have multiple layers, are clean, and dry, the CDC and WHO currently say they are a choice of last resort if N95 nor surgical masks are not available. However, this is in the context of situations where social distancing (at least 6') can be maintained, hands are cleaned frequently, you're not in a large group, and you're not indoors with others for extended periods of time. I can't see any of these other 4 things being maintained in most school settings.

Even if communities are at the yellow or orange levels of risk indicating that in-person classes are possible, these factors seemed to line up to create a situation which is going to drive communities toward red levels.

======================================

I also did quite a bit of reading on mortality rates. There's some cool math in the modelling.

Most people that work in this field seem to find mortality rates during an epidemic almost irrelevant. They are numbers best suited to discuss once the epidemic is over and all infections have been resolved one way or the other. When there is a significant delay in the time of infection and the time of death, the unresolved infections/cases can leave significant undercounts of deaths during the epidemic making mortality rates misleading.

A common way of measuring mortailty is with case fatality rates/ratios (CFR), where the numerator is the deaths and the dominator is the number of defined cases. Early in an epidemic, most cases are people with severe symptoms so mortality rates are biased towards the high side. Furthermore, without significant testing, many infected people are never identified so case counts are far lower than they should be.

To account for this they often use a infection fatality rate (IFR) where the denominator is the number of defined cases plus an estimate of how many infections have not been identified. The math and assumptions involved in making this estimate are interesting, but it's still an estimate. Further assumptions/models are required to account for the issues related to the status of unresolved cases while in the midst of the epidemic.

Identifying deaths due to a virus is also not clear cut. Comorbidities create confounding situations that cannot be resolved. The WHO publishes guidelines on how to fill out death certificates when there are comorbidities to try to create some uniformity to allow for comparisons, but the numbers are not absolute and never will be.

Calculating deaths on a per capita basis during an epidemic seemed to be the preferred over CFR or IFR measures, but are still of marginal utility to those working to end epidemics. Differences in age distributions, rates of comorbidities, access to healthcare, testing (and lack thereof) to identify the virus as a contributing factor, etc. in different communities/countries make even deaths/capita misleading.

==========================================

My impression now is that we let the cat out of the bag this spring. The community spread we have now means that how we handle this from this point on can't be the same as other countries who were able to tame it early. This is going to have real consequences in lives lost and the need for many to live with life-altering complications.

What works in countries with very low levels of virus in the communities is not going to work in most places in the U.S. Contract tracing is no longer a realistic tool. Being in groups indoors even with masks and social distancing is going to have very different outcomes in the U.S. than in those other countries.

Over many years, things will settle out. Vaccines and naturally occuring infections resulting in "herd" immunity will eventually reduce the impact of COVID-19, but between now and then the road we're on is going to be far more unpleasant. Will it be worth it? It's going to have a negative impact on our economy, people are going to die at a higher rate, many people are going to have to learn with life-altering complications, etc. but most people will go on with their lives. It will become another "flu" we deal with. It will fade into the background. After a while the majority of us will not be directly affected. We will forget those we lost and the sacrifices many made. We will accept the situation and blithely move on.

In the meanwhile we will suffer in a multitude of ways while blaming others for our suffering.

... I know. tl;dr
 
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JAVMAN83

Well-known member
Madman,

Excellent post! Except for the statement regarding that other countries have gotten a handle on this, everything else comports with what I came to believe about the virus back in March. No amount of so-called lockdowns or our ridiculous mask-wearing or social-distancing efforts have made or will make much of a diffetence given how small the particulate size the of the virus. It would be impossible financially for everyone to afford, IF IT WERE AVAILABLE, the PPE to effectively cover the orifices of the body through which the virus can enter. This may depress the hell out of some people who have believed the government mantra that has been promoted over the last 5 months, but truth is truth. Learn it & accept it.

The part about other countries having successfully dealt with virus - that is pure fiction. I've been watching reports on BBC, NHK, DW, & a whole host of other news sites, & what is clear is that they are going through their own second waves, and like us, will go through multiple waves over time before effective vaccines & herd immunity are achieved. None of us knows whether we will survive this current era, including my sorry butt. However, we cannot as a society put the future on hold. We need to go about our daily lives as normally as possible.
 

yj_runfan

Well-known member
The goal of stopping COVID-19 cases is not the appropriate goal. The goal is simply twofold, to protect the people who are going to have a serious problem or die, that’s the high-risk population, and to stop hospital overcrowding. There should never be and there is no goal to stop high school / college students from getting an infection they have no problem with. Locking down healthy people is just irrational.
From what I've heard, they aren't worried much about the effect of Covid on the students. They are most worried about the students taking the infection home and into their social circles.
 

Percidae

Member
The more reading of research I do, the more doubtful I become about holding in-person classes. A friend who is a doctor was talking to be about how useless face masks are relative to viruses, even N95 masks. I didn't believe him, so I started reading the research articles that are available online. Virus particles are on the orderof 0.1 micron in diameter. In aerosol form they are 0.5 to 2.0 micron which pass through masks and as the moisture evaporates, they become so light that they ride air currents more than fall to the ground like the droplets do. Surgical masks are much less effective than N95 masks, and cloth masks are one-third as effective as surgical masks and nearly useless against aerosols.

We are still early in the epidemic so there is still a lot of hypothesizing and not a lot of definite answers, but there seems to be a general consensus that the virus can be transmitted by touch, droplets, and aerosols; though, the efficacy of each modality isn't known.

Cloth masks do seem to reduce the distance droplets travel, but are almost completely ineffective against aerosols. As masks become damp, they become even less effective. Teachers/students working in buildings that are not air-conditioned and are prohibited against using fans (which would simply spread droplets and aerosols over a greater distance) are going to be sweating a lot. Their masks are going to get wet and even less effective.

The masks also serve as collection devices for virus particles; hence, without proper handling techniques they can serve to increase the chance of transmission by touch. Furthermore, if they are not cleaned on a regular basis this situation becomes much worse. Viruses can remain "active" for at least a couple days on most surfaces including masks.

When cloth masks have multiple layers, are clean, and dry, the CDC and WHO currently say they are a choice of last resort if N95 nor surgical masks are not available. However, this is in the context of situations where social distancing (at least 6') can be maintained, hands are cleaned frequently, you're not in a large group, and you're not indoors with others for extended periods of time. I can't see any of these other 4 things being maintained in most school settings.

Even if communities are at the yellow or orange levels of risk indicating that in-person classes are possible, these factors seemed to line up to create a situation which is going to drive communities toward red levels.

======================================

I also did quite a bit of reading on mortality rates. There's some cool math in the modelling.

Most people that work in this field seem to find mortality rates during an epidemic almost irrelevant. They are numbers best suited to discuss once the epidemic is over and all infections have been resolved one way or the other. When there is a significant delay in the time of infection and the time of death, the unresolved infections/cases can leave significant undercounts of deaths during the epidemic making mortality rates misleading.

A common way of measuring mortailty is with case fatality rates/ratios (CFR), where the numerator is the deaths and the dominator is the number of defined cases. Early in an epidemic, most cases are people with severe symptoms so mortality rates are biased towards the high side. Furthermore, without significant testing, many infected people are never identified so case counts are far lower than they should be.

To account for this they often use a infection fatality rate (IFR) where the denominator is the number of defined cases plus an estimate of how many infections have not been identified. The math and assumptions involved in making this estimate are interesting, but it's still an estimate. Further assumptions/models are required to account for the issues related to the status of unresolved cases while in the midst of the epidemic.

Identifying deaths due to a virus is also not clear cut. Comorbidities create confounding situations that cannot be resolved. The WHO publishes guidelines on how to fill out death certificates when there are comorbidities to try to create some uniformity to allow for comparisons, but the numbers are not absolute and never will be.

Calculating deaths on a per capita basis during an epidemic seemed to be the preferred over CFR or IFR measures, but are still of marginal utility to those working to end epidemics. Differences in age distributions, rates of comorbidities, access to healthcare, testing (and lack thereof) to identify the virus as a contributing factor, etc. in different communities/countries make even deaths/capita misleading.

==========================================

My impression now is that we let the cat out of the bag this spring. The community spread we have now means that how we handle this from this point on can't be the same as other countries who were able to tame it early. This is going to have real consequences in lives lost and the need for many to live with life-altering complications.

What works in countries with very low levels of virus in the communities is not going to work in most places in the U.S. Contract tracing is no longer a realistic tool. Being in groups indoors even with masks and social distancing is going to have very different outcomes in the U.S. than in those other countries.

Over many years, things will settle out. Vaccines and naturally occuring infections resulting in "herd" immunity will eventually reduce the impact of COVID-19, but between now and then the road we're on is going to be far more unpleasant. Will it be worth it? It's going to have a negative impact on our economy, people are going to die at a higher rate, many people are going to have to learn with life-altering complications, etc. but most people will go on with their lives. It will become another "flu" we deal with. It will fade into the background. After a while the majority of us will not be directly affected. We will forget those we lost and the sacrifices many made. We will accept the situation and blithely move on.

In the meanwhile we will suffer in a multitude of ways while blaming others for our suffering.

... I know. tl;dr
Everything you are saying may end up being 100% true. However, I have read and heard things that contradict almost everything you are saying as well. So what are we to do? To date we are trying to put up the good fight. Or at least some kind of fight. Based on your synopsis, this is futile. So do we try the "rip the bandaid off" quickly strategy? The time to have done this would have been right off the bat. Let it burn through quickly and be done with it. Fighting the good fight is slow, agonizing and may very well do long term harm to our society.

I am more hopeful. I think we will be able to make it through to a viable vaccine without overwelming casualties or lasting damage to our ecomony. The death rate will end up being far lower than most people think as we gain experience and theraputics. The problem is that there is so much entrenched fear that has been sown over the past few months, I am not sure it is possible for most people to move on in the near term.
 

madman

Well-known member
I will admit that I am pretty bummed right now, but we've got to face reality so that we can act accordingly. If cloth masks only prevent 10% of possible transmission through droplets when they are dry and worn properly and become nearly useless when damp or not worn properly, then we need to make sure that students and teachers bring enough masks each day that they can change them and know how to properly handle them so that we don't increase transmission due to touch.

If we didn't need schools for childcare, would there still be the push to have in-person classes?

If we didn't need schools for the socializing/mental health issues, would there still be the push to have in-person classes?

Issues like these are certainly pushing us in a direction (large indoor gatherings with poor ventilation for extended periods of time) that we would not otherwise go.

We need to realize that masks are giving people a false sense of security that result in them being less likely to maintain social distancing when in groups.

We need to realize that most people don't know how, and certainly don't follow, proper procedures for wearing/handling of masks.

I think we still need mitigating actions to prevent our limited healthcare resources from being overwhelmed, leading to complications from other on-going health issues.

At this point we've pissed in our pool. It's going to have unpleasant consequences that mean what will work in our situation aren't the same things that may have worked in other communities/countries where community spread is far lower than it is here.

Spain had 113 deaths in from July 5th to August 4th (30 days). We have that many about every 3 hours. Their population is about 1/7th of the U.S. population, but there is no way to say their situation is similar to ours.
 

psycho_dad

Well-known member
The mask thing is hard to figure. My personal experience has been that masks make people socially distance better. However, I work with people one or two at a time. The mask seems to make you think, "I should be a little further away." Don't shake their hand. I can see how in a large group, it makes people less cautious though.

We better hope that it does not adversely affect kids, cuz it seems like we are getting ready to throw a bunch of them into a petri dish. First teacher that dies will bring this to a screeching halt don't you think?
 

madman

Well-known member
I don't think "a" teacher's death is going to bring it to a halt since we aren't going to be able to trace a lone death back to the school setting.

However, since students and teachers will bring home anything thing they might have picked up in school, I do believe we're going to see numbers within communities rise rapidly in settings where classes are predominantly in school.

Clusters of teachers within a school with significant adverse reactions related to COVID will definitely bring things to a halt locally. If it happens in many locales, then it will result in broad scale halts. The problem is the delay between infections and tragic outcomes. By the time we're aware of a problem, the genie's already out of the bottle.

I am ready to go back to school understanding these risks. However, I am not married and don't have kids, so I am not bringing home these problems to others. I don't have ailing elderly relatives that are nearby. I don't travel much and don't even go out much. We are all vectors, but my magnitude is small.
 

CC Track Fan

Active member
Spain had 113 deaths in from July 5th to August 4th (30 days). We have that many about every 3 hours. Their population is about 1/7th of the U.S. population, but there is no way to say their situation is similar to ours.
It is called herd immunity. Look at the NE states that got hit early one. Positive test percentage for last 7 days.
Connecticut - 1.2%
Maine - .8%
Massachusetts - 3.0%
New Hampshire - 1.8%
New Jersey - 1.5%
New York - 1.0%
 

madman

Well-known member
It is called herd immunity. Look at the NE states that got hit early one. Positive test percentage for last 7 days.
Connecticut - 1.2%
Maine - .8%
Massachusetts - 3.0%
New Hampshire - 1.8%
New Jersey - 1.5%
New York - 1.0%
Interesting claim. Do you have any evidence? Experts have indicated that 70% of the population will need to have been infected to achieve herd immunity for COVID-19. I haven't heard anyone, except possibly you, claim infection rates are anywhere near that.

Even in NYC, ~230,000 cases have been identified. Some people think the number of unverified infections might be has high as 10 times the number of verified cases. That would still be a long way from 70% of the population.

You're going to need to come up with a better explanation or some evidence.
 

CC Track Fan

Active member
Interesting claim. Do you have any evidence? Experts have indicated that 70% of the population will need to have been infected to achieve herd immunity for COVID-19. I haven't heard anyone, except possibly you, claim infection rates are anywhere near that.

Even in NYC, ~230,000 cases have been identified. Some people think the number of unverified infections might be has high as 10 times the number of verified cases. That would still be a long way from 70% of the population.

You're going to need to come up with a better explanation or some evidence.
First I will throw it back to you what other reason could it be? If it is masks and SD then why is California which has had the mandates just as long not doing just as well. Some of the biggest mask wearing countries in the world (Japan and Philippians) that didn't have it early on are now getting hit harder now.
1596650558076.png1596650607016.png
The CDC estimate is 10 to 24 times higher than the actual case count for the US. It is not hard to believe that the early places like NYC have a much higher multiple since they got hit with it early when testing was much more limited. Plus if it was in Ohio in January it would not be surprising if it was in NYC in December so how many people were exposed before testing even began.

Plus there is a thought process that some signs of herd immunity will begin as low as 20%. Here is one article that thinks could be 20%. Obviously 20% isn't going to wipe it out but will greatly slow the infection rate which is being seen in NE US and many eastern EU countries while the western EU countries which were hit much softer early on are now seeing increases. I don't know of any area that was hit hard early and then was hit hard again when other places that were not hit hard early had their increases.

Clearly I don't know for certain but there is evidence that herd immunity could be a big factor in the decreases in cases/deaths in the early hard it areas.
 

madman

Well-known member
I don't know that anyone knows for sure why numbers are increasing in Japan, but Japanese media is placing the blame on complacency since Japan cancelled their state of emergency on May 25th. Also, as President Trump likes to remind people additional testing increases the number of cases. It could be that Japan's testing rate has increased.

With regard to the Northeast U.S. I am guessing that due to the severity of the problem they experienced, there is less complacency. Does the higher rate of infection there reduce the portion of the population susceptible infections? I don't doubt that, but based on what I have read they are a long way from herd immunity.

Something else needs to explain the difference between why Japan's (pop 126MM) total number of deaths just topped 1000 and our's (pop 328MM) just topped 160,000. Japan just had 2000 new cases reported on Monday, a significant new record for them. They have about the same number of cases that we have deaths each day. ~3000 people died in the 9-11 attacks. In the US that happens every three days now.

Note that Spain's rate of new cases went from 334/day at the end of June when they eliminated their state of emergency to 5760/day yesterday. This would seem to argue against significant herd immunity being present.

Who really cares, though. It's just going to go away.
 
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Something else needs to explain the difference between why Japan's (pop 126MM) total number of deaths just topped 1000 and our's (pop 328MM) just topped 160,000.
The poor overall health of U.S. population? Japan does not have 60% of the population obese, diabetes, high blood pressure, etc. do they? I wonder if their general population handled the virus better because they do not have the enormous pre-existing health problems?
 

madman

Well-known member
A fair point. It will be interesting to see as time goes on how strong the linkage is between obesity rate and death rate from country to country.
 

mathking

Active member
Madman, here is a diagram one of my former students who is now an engineer studying mask effectiveness and design created to explain to my robotics team about why even cloth masks have an important inhibitive effect. It explains how our thinking gets two dimensional when we think about mask openings when it shouldn't. At least as important as stopping particles is the ability of a mask reduce the velocity of particles penetrating them, which reduces how far they spread.
MaskPenetrationDiagram.jpg

The general point is that even a simple cloth mask can reduce the effective velocity of aerosolized particles by 30-80% depending on the cloth, and that even a simple cloth mask will intercept a not-insignificant percentage of the virus-laden particles it encounters.

Your points about wetness and cleaning are important. His recommendation is wool masks. Non-woven fabrics protective effects are not changed much by moisture. Cleaning is essential to protect the wearer. Regular washing is really important. It would really be best for kids to have two masks and to switch mid day. (Putting the used mask in a ziploc bag.)

I have spent most of the last six months working on various projects to study, design and test masks. But I am by training a statistical modeler. The data is becoming more and more clear that masks provide significant benefit. Both with direct testing, re-analyzing old "masks are not effective" studies to understand what they really said and with statistical looks at spread where mask wearing is more and less effective. The real problem is not that masks are ineffective, it is that if you spend several hours with an infected person indoors, even though masks are significantly reducing the amount of virus you encounter, it may well not be enough.
 

Running Man 101

Active member
I don't think "a" teacher's death is going to bring it to a halt since we aren't going to be able to trace a lone death back to the school setting.

However, since students and teachers will bring home anything thing they might have picked up in school, I do believe we're going to see numbers within communities rise rapidly in settings where classes are predominantly in school.

Clusters of teachers within a school with significant adverse reactions related to COVID will definitely bring things to a halt locally. If it happens in many locales, then it will result in broad scale halts. The problem is the delay between infections and tragic outcomes. By the time we're aware of a problem, the genie's already out of the bottle.

I am ready to go back to school understanding these risks. However, I am not married and don't have kids, so I am not bringing home these problems to others. I don't have ailing elderly relatives that are nearby. I don't travel much and don't even go out much. We are all vectors, but my magnitude is small.
If that happens then the masks and social distancing is meaningless. After looking at the "bump" curve, it looks like the backside of a standard mass infection curve.
 

CC Track Fan

Active member
Madman, here is a diagram one of my former students who is now an engineer studying mask effectiveness and design created to explain to my robotics team about why even cloth masks have an important inhibitive effect. It explains how our thinking gets two dimensional when we think about mask openings when it shouldn't. At least as important as stopping particles is the ability of a mask reduce the velocity of particles penetrating them, which reduces how far they spread.
View attachment 8969

The general point is that even a simple cloth mask can reduce the effective velocity of aerosolized particles by 30-80% depending on the cloth, and that even a simple cloth mask will intercept a not-insignificant percentage of the virus-laden particles it encounters.

Your points about wetness and cleaning are important. His recommendation is wool masks. Non-woven fabrics protective effects are not changed much by moisture. Cleaning is essential to protect the wearer. Regular washing is really important. It would really be best for kids to have two masks and to switch mid day. (Putting the used mask in a ziploc bag.)

I have spent most of the last six months working on various projects to study, design and test masks. But I am by training a statistical modeler. The data is becoming more and more clear that masks provide significant benefit. Both with direct testing, re-analyzing old "masks are not effective" studies to understand what they really said and with statistical looks at spread where mask wearing is more and less effective. The real problem is not that masks are ineffective, it is that if you spend several hours with an infected person indoors, even though masks are significantly reducing the amount of virus you encounter, it may well not be enough.
That is great if you have scientific proof that it works. You should share it with 3M so they can remove this label from the N95 masks.

1596725925320.png
 

madman

Well-known member
Madman, here is a diagram one of my former students who is now an engineer studying mask effectiveness and design created to explain to my robotics team about why even cloth masks have an important inhibitive effect. It explains how our thinking gets two dimensional when we think about mask openings when it shouldn't. At least as important as stopping particles is the ability of a mask reduce the velocity of particles penetrating them, which reduces how far they spread.
View attachment 8969

The general point is that even a simple cloth mask can reduce the effective velocity of aerosolized particles by 30-80% depending on the cloth, and that even a simple cloth mask will intercept a not-insignificant percentage of the virus-laden particles it encounters.

Your points about wetness and cleaning are important. His recommendation is wool masks. Non-woven fabrics protective effects are not changed much by moisture. Cleaning is essential to protect the wearer. Regular washing is really important. It would really be best for kids to have two masks and to switch mid day. (Putting the used mask in a ziploc bag.)

I have spent most of the last six months working on various projects to study, design and test masks. But I am by training a statistical modeler. The data is becoming more and more clear that masks provide significant benefit. Both with direct testing, re-analyzing old "masks are not effective" studies to understand what they really said and with statistical looks at spread where mask wearing is more and less effective. The real problem is not that masks are ineffective, it is that if you spend several hours with an infected person indoors, even though masks are significantly reducing the amount of virus you encounter, it may well not be enough.
The problem with aerosols is that they can float on the natural air currents for hours. The are unaffected by gravity relative to other forces. The initial velocity isn't relevant beyond a few seconds.

I wish I could find the research article I was reading. It had awesome graphics that showed initial dispersions in three dimensions with no mask, N95 masks, surgical masks, and simple cloth masks. It also had models with the same in a car, a hospital room with multiple beds, and ... I can't remember the 3rd setting.
 

madman

Well-known member
That is great if you have scientific proof that it works. You should share it with 3M so they can remove this label from the N95 masks.

View attachment 8971
Aren't N95 masks intended to protect the wearer not other people? The valve is one way - it essentially allows unfiltered air to be expelled while preventing doctors/workers from breathing in contaminated air. They do restrict velocities per Mathking's point, but they still allow significant aerosols into the environment.

What we don't know yet is the effectiveness of aerosols versus droplets in the transmission of COVID-19.
 
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mathking

Active member
A couple quick thoughts. Medical N95 masks are two way. Madman, when was the research you were reading published and what were the results? A lot of the masks have almost no effect research I have read actually shows effect, just not enough to justify use in a medical or research setting. On the subject of velocity for aerosols, it actually matters a great deal. Somewhere I have a Brownian motion model that shows this to great effect. It doesn't matter in a setting with no ventilation. But in a ventilated room it actually matters a fair amount. The slower it is moving when it is expelled the easier it is captured by ventilation. In any event, it is not clear right now what percentage of transmission is large droplets vs. aerosols, but the research (both direct and indirect) that has been done in the past few months shows pretty clearly that there is a beneficial effect from mask wearing.
 

madman

Well-known member
From the CDC website

"An N95 respirator with an exhalation valve does provide the same level of protection to the wearer as one that does not have a valve. The presence of an exhalation valve reduces exhalation resistance, which makes it easier to breathe (exhale). Some users feel that a respirator with an exhalation valve keeps the face cooler and reduces moisture build up inside the facepiece. However, respirators with exhalation valves should not be used in situations where a sterile field must be maintained (e.g., during an invasive procedure in an operating or procedure room) because the exhalation valve may allow unfiltered exhaled air to escape into the sterile field."

A pdf file from the CDC explaining the difference between a surgical mask and an N95 mask
  • N95 respirators reduce the wearer’s exposure to airborne particles, from small particle aerosols to large droplets. N95 respirators are tight-fitting respirators that filter out at least 95% of particles in the air, including large and small particles.
  • Not everyone is able to wear a respirator due to medical conditions that may be made worse when breathing through a respirator. Before using a respirator or getting fit-tested, workers must have a medical evaluation to make sure that they are able to wear a respirator safely.
  • Achieving an adequate seal to the face is essential. United States regulations require that workers undergo an annual fit test and conduct a user seal check each time the respirator is used. Workers must pass a fit test to confirm a proper seal before using a respirator in the workplace.
  • When properly fitted and worn, minimal leakage occurs around edges of the respirator when the user inhales. This means almost all of the air is directed through the filter media.
  • Unlike NIOSH-approved N95s, facemasks are loose-fitting and provide only barrier protection against droplets, including large respiratory particles. No fit testing or seal check is necessary with facemasks. Most facemasks do not effectively filter small particles from the air and do not prevent leakage around the edge of the mask when the user inhales.
  • The role of facemasks is for patient source control, to prevent contamination of the surrounding area when a person coughs or sneezes.  Patients with confirmed or suspected COVID-19 should wear a facemask until they are isolated in a hospital or at home. The patient does not need to wear a facemask while isolated.
I apologize for not being able to find the link the research article I was reading. It's very frustrating to not be able to find it. However, they did find that cloth face masks were less than 1/3 as efficient as surgical masks at controlling droplets and nearly useless against aerosols.

With regard to teachers wearing N95 masks, it's not as easy as just providing each teacher with one every day. Fit testing, seal checking, medical evaluations to ensure they can be worn, etc. are significant added steps, responsibilities, and costs. Can they all be done? Yep. Should they be done? That is entirely another question.

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Do I believe that a cloth mask provides "some" protection to the wearer? Yes, but I now think that it's far less than what I had believed.

Do I believe that a cloth mask provides "some" protection to others around the wearer? Again, the answer is yes, but I now think the benefit is much smaller that commonly believed.

As a statistician, you have to be aware that anecdotal evidence related to the effectiveness of face masks is hardly convincing of a cause/effect relationship.

I do believe that wearing a face mask is a tool in our arsenal, but it isn't near as powerful as some would think. I am concerned that there is an over-emphasis on wearing cloth face masks that is generating a false sense of security among those who do wear them which in turn leads to riskier behaviors.

We need to wear them, clean and dry. We need to learn how to handle them. We still need to socially distance, clean our hands regularly, avoid touching our eyes, nose, and mouth, and avoid large groups especially indoors.

This isn't helping

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