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In God's name. What have I just seen. Can the PPRuNe community do something?

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In God's name. What have I just seen. Can the PPRuNe community do something?

Old 2nd Apr 2020, 12:44
  #41 (permalink)  
 
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Originally Posted by VP959 View Post
I've looked and can find absolutely nothing to support that view for this particular virus. I can't even find any research that's looked at the minimum viral titre required to cause infection. The suspicion is that it takes a lot more than one virion to cause infection for this particular virus, but how many more than one seems to be anyone's guess. Part of the problem seems to be that viral replication may be imperfect, so some virions may not be able to cause infection, although I can't find any data that suggests what proportion that may be.
Pity. It would appear to have supported the argument in favour of masks !!!
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Old 2nd Apr 2020, 13:42
  #42 (permalink)  
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occasional - The paper I read on the internet this week was quite definite, possibly based on results obtained in China however it would appear that the jury is still out in other places, like Italy for example.

https://www.newscientist.com/article...ovid-19-worse/
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Old 2nd Apr 2020, 13:58
  #43 (permalink)  
 
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Can someone help me with the 'viral load' issue? If a single virus invades a cell it manufactures multiple copies of itself and then bursts the cell. How is this less of a problem than 10/100/1000 of the little sods doing the same thing initially? I assume the time between cell invasion and going on viral holiday is only a matter of hours. So a day after offering a home to a single virus the conditions are the same a someone ingesting a larger load. So to be effective a facemask must prevent every single virus entering the lungs. How is this acheived with a loose fitting facemask?
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Old 2nd Apr 2020, 14:19
  #44 (permalink)  
 
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Why do people driving cars, on their own, wear masks? And I don't mean delivery drivers. What's the point?
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Old 2nd Apr 2020, 15:00
  #45 (permalink)  
 
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Originally Posted by Tone View Post
Can someone help me with the 'viral load' issue? If a single virus invades a cell it manufactures multiple copies of itself and then bursts the cell. How is this less of a problem than 10/100/1000 of the little sods doing the same thing initially? I assume the time between cell invasion and going on viral holiday is only a matter of hours. So a day after offering a home to a single virus the conditions are the same a someone ingesting a larger load. So to be effective a facemask must prevent every single virus entering the lungs. How is this acheived with a loose fitting facemask?
There seem to be a few points that may be relevant. Firstly, it seems that not every virion (virus particle) can actually penetrate a cell, plus some seem to not be able to cause it to replicate. Also, the body's first line of defence is a mucous layer that tries to move anything we inhale to somewhere it can't get a hold and cause infection (often just gets swallowed). This virus can also only infect certain types of cell within our airways, so unless it gets close to one of those cells it can't cause infection.

The result of all this seem to be that there is probably a minimum number of virions needed to cause infection. It's not clear how many that is, could be a hundred, could be a thousand, could be ten thousand or more. The suggestion at the moment is that the number required is towards the lower end of this scale, rather than the upper end.

A mask only needs to reduce the concentration of breathed in virions by a bit to make a difference, although that depends very much on the airborne risk. Outdoors, the risk is going to be very low, even if within a metre or two of someone else, just because air movement will tend to disperse and dilute anything pretty quickly. Indoors, with others who might be infective, the risk is likely to be greater, but will be a function of time. Someone spending hours in a potentially infective environment will be at much greater risk than someone only there for a few minutes.

Wearing masks when they can have little or no effect seems pointless, but there may be a psychological positive impact, by making people feel safer and less anxious. The snag is that risk compensation may then kick in and they may start taking greater risks with hand hygiene, thinking that the mask will keep them safe, when it won't do much to reduce hand transferred contamination.
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Old 2nd Apr 2020, 15:55
  #46 (permalink)  
 
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Originally Posted by VP959 View Post
There seem to be a few points that may be relevant. Firstly, it seems that not every virion (virus particle) can actually penetrate a cell, plus some seem to not be able to cause it to replicate. Also, the body's first line of defence is a mucous layer that tries to move anything we inhale to somewhere it can't get a hold and cause infection (often just gets swallowed). This virus can also only infect certain types of cell within our airways, so unless it gets close to one of those cells it can't cause infection.

The result of all this seem to be that there is probably a minimum number of virions needed to cause infection. It's not clear how many that is, could be a hundred, could be a thousand, could be ten thousand or more. The suggestion at the moment is that the number required is towards the lower end of this scale, rather than the upper end.

A mask only needs to reduce the concentration of breathed in virions by a bit to make a difference, although that depends very much on the airborne risk. Outdoors, the risk is going to be very low, even if within a metre or two of someone else, just because air movement will tend to disperse and dilute anything pretty quickly. Indoors, with others who might be infective, the risk is likely to be greater, but will be a function of time. Someone spending hours in a potentially infective environment will be at much greater risk than someone only there for a few minutes.

Wearing masks when they can have little or no effect seems pointless, but there may be a psychological positive impact, by making people feel safer and less anxious. The snag is that risk compensation may then kick in and they may start taking greater risks with hand hygiene, thinking that the mask will keep them safe, when it won't do much to reduce hand transferred contamination.
Given the conflicting information about masks, humidity and temperature, one simple alternative or additional measure would be for supermarkets and shops to up the air change rate indoors. At least in the UK where outdoor temperatures are more or less comfortable now heating could be dispensed with so simply get the fresh air in and ‘used’ air out, ideally through high level or roof vents well away from pedestrians.
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Old 2nd Apr 2020, 17:50
  #47 (permalink)  
 
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There was a brief item I heard yesterday on a news break, I think on the radio, that Austria is mandating that anyone who goes out in public must wear a mask.

If it turns out that mandating a mask of some sort for EVERYONE who goes outside their home could have avoided this whole lockdown thing there is going to be a mighty kerfuffle, though I guess the authorities will come up with some sort of 'pass the buck' excuse.
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Old 2nd Apr 2020, 17:55
  #48 (permalink)  
 
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Just seen a classic example of how wearing a mask and gloves, without adequate training, can massively increase the risk. BBC news item, talking about PPE, showing a lady wearing mask and gloves on a checkout. What does she do? Put both gloved hands up to her face to adjust her mask. Not her fault, she clearly wasn't trained, but gloves transmit infection more effectively than bare hands, in this case, and putting both hands to her face was a pretty sure fire way to transfer contamination to her mouth, nose or eyes.
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Old 3rd Apr 2020, 00:02
  #49 (permalink)  
 
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Originally Posted by Loose rivets View Post
There is more common sense talked on PPRuNe that in Parliament.
Then, may God help us!
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Old 3rd Apr 2020, 00:04
  #50 (permalink)  
 
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According to a health department microbiologist on a webinar for health professionals last night, a problem with wearing a P2 mask full time, is that if it gets damp from the user's breath, and then viruses land on it from outside, they can migrate straight through.
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Old 3rd Apr 2020, 00:09
  #51 (permalink)  
 
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The man in the black suit is Armin Laschet. Chief minister of north rhine westphalia, Germany.


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Old 3rd Apr 2020, 03:26
  #52 (permalink)  
 
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Conspiracy theories aren't my thing, but in this case it does seem likely that WHO/CDC/etc were trying to stop a run on unavailable masks by individuals by saying they're useless or worse.

Here are some facts which I found very useful about how masks work (from the CDC). Counterintuitively, they work BETTER for really tiny (<300nm) particles. The 300nm size is chosen for the N95 criterion because it's the HARDEST size to trap.

There seem to be lots of people of internet forums (like this one) trying to come up with reasons why masks are worse than useless. I don't understand their motivation. If they "only" reduce the probability of infection (or its nastiness when it happens) by 95%, that sounds like a pretty good deal to me. Why on earth wouldn't you (assuming you have access)?

https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95
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Old 3rd Apr 2020, 08:25
  #53 (permalink)  
 
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Originally Posted by n5296s View Post
Conspiracy theories aren't my thing, but in this case it does seem likely that WHO/CDC/etc were trying to stop a run on unavailable masks by individuals by saying they're useless or worse.

Here are some facts which I found very useful about how masks work (from the CDC). Counterintuitively, they work BETTER for really tiny (<300nm) particles. The 300nm size is chosen for the N95 criterion because it's the HARDEST size to trap.

There seem to be lots of people of internet forums (like this one) trying to come up with reasons why masks are worse than useless. I don't understand their motivation. If they "only" reduce the probability of infection (or its nastiness when it happens) by 95%, that sounds like a pretty good deal to me. Why on earth wouldn't you (assuming you have access)?

https://blogs.cdc.gov/niosh-science-blog/2009/10/14/n95
For the simple reasons that few people will know how to properly fit a mask to their face initially (as in that photo above) and even more will end up touching their face more often when wearing one, and hand to face contact is a very effective transmission route, especially in any area where many people may have touched surfaces.

Masks are fine, and can reduce the transmission rate. However, if wearing a mask results in increasing the risk from hand to face transmission, then the mask could be making things worse, rather than better.

IF people can be trained to both wear a mask correctly (i.e.NOT as the Chief Minister of North Rhine Westphalia, Germany, is doing in the above photo) and IF people don't touch their face whilst they are wearing a mask (especially if they are also wearing surgical gloves) then they would almost certainly make some difference.

Last edited by VP959; 3rd Apr 2020 at 10:09. Reason: typo - missed a critical "don't" out
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Old 3rd Apr 2020, 09:03
  #54 (permalink)  
 
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Our next door neighbour popped two homemade masks through our letterbox last night. Nice thought, but they are just two pleated rectangles of thick cotton - when you put them on, there are enormous gaps on either side and around the nose. I really can see no benefit in them at all, unless, I suppose you already have the virus, and it may stop the spread of infection if you sneeze.
Unfortunately, every time I go out for my daily walk, I will now have to wear the confounded thing while I walk pass her house, so as not to upset her.
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Old 3rd Apr 2020, 09:13
  #55 (permalink)  
 
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Originally Posted by wowzz View Post
Our next door neighbour popped two homemade masks through our letterbox last night. Nice thought, but they are just two pleated rectangles of thick cotton - when you put them on, there are enormous gaps on either side and around the nose. I really can see no benefit in them at all, unless, I suppose you already have the virus, and it may stop the spread of infection if you sneeze.
Unfortunately, every time I go out for my daily walk, I will now have to wear the confounded thing while I walk pass her house, so as not to upset her.
What assurance do you have that these home made masks are not already contaminated with the virus, though?

I admire the spirit of goodwill that is being demonstrated by so many, but there is a very real risk that things like this could be very effective transmission vectors. All it would take is for one volunteer to be infected, but asymptomatic, and they could spread infection to several other households, effectively become "super spreaders".

For a couple of weeks or so now we've adopted a system where nothing comes into the house unless it's been disinfected. That means we wash the outside of milk bottles on the doorstep before bringing them into the house, we wipe down the outside of all non-porous packaging on food and groceries before packing them away, we wash all fruit and vegetables thoroughly as we unpack them and we try to leave any porous packages (cardboard etc) outside, ideally in the sun, for a few hours before bringing them into the house. Our post box is outside the house, and no letters, etc, come into the house via that route (and they get quarantined outside like any other porous material). The surfaces that anything has rested on, and our hands, and anything they may have touched, gets washed, too.
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Old 3rd Apr 2020, 10:01
  #56 (permalink)  
 
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In retirement I am becoming ever so suspectful of everyone for every reason . Any chance that suppliers & providers might be cashing in, big time, on our overall ignorance ? I am siding with the "mask -up " brigade if for no other reason than everyone else seems to . But, local pharmacist was offering 50c masks for 5 euros each. Looking at my fake rolex, he suggested a box of really fancy ones that would normally retail at E15 for E150 !! Nothing better to do but dodge the virus on my permitted shop for essentials, I swung him along by trying out a sample (probably infected) & nearly fell for the sale of one (E5) because it reminded me of donning on masks & Regulators & establishing comms. This IS fun , me thought & caught sight of his assistant , paricularly lovely young thang giving me an admiring glance. Fell for it, bought it , donned it ( in the car) and headed off to Lidles but looking much trendier than the only other driver on an otherwise deserted Cypriot road. Stafe safe out there people.
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Old 3rd Apr 2020, 12:19
  #57 (permalink)  
 
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Originally Posted by gearlever View Post
The man in the black suit is Armin Laschet. Chief minister of north rhine westphalia, Germany.


You may laugh, but I've seen two people do exactly the same in the town I live.
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Old 3rd Apr 2020, 12:25
  #58 (permalink)  
 
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One reason people tend to wear masks in a way that makes them virtually useless is if they wear glasses. You quickly realise that failing to shape the noseband to properly fit across the nose leads to exhaled breath misting up glasses. The proper fix is the fit the mask properly, but the bodge often adopted is to just pull the mask clear of the nose.
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Old 3rd Apr 2020, 15:10
  #59 (permalink)  
 
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To amplify VP959's point - the masks as supplied look like this, with a metal strip bonded to the top:



To use, the band should be pressed and formed to follow the contours of the face around the nose like this:



PDR

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Old 3rd Apr 2020, 19:19
  #60 (permalink)  
 
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Not if you put the mask on upside down it doesn't.
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