What I would like to know is what % of people are infected by air borne droplets which a mask or face covering might inhibit, and what % get it from touching infected surfaces which is so much more difficult to constrain.
There is @BenCotto - my daughter was quoting it the other day. Its by an American University (maybe Harvard, but not sure). The conclusion was that majority transmission is airborne, very little via contaminated surfaces ......so disinfecting your groceries is a waste of time, but wearing a face covering can really help.
I posted a while back on masks - the research into how effective they are in 'the real world' is so difficult to gauge, as (obviously) how can you tell who has the virus anyway? You may wear a mask and always be in places where the virus isn't. There is information on how effective certain masks are at stopping droplets from penetrating them in test environments. So a mask itself can be judged/graded. A mask is also only as effective as the protocol used when using it - see 'How to wear a face covering' here https://www.gov.uk/government/publications/face-coverings-when-to-wear-one-and-how-to-make-your-own/face-coverings-when-to-wear-one-and-how-to-make-your-own
..and this is what WHO says:
...I doubt many people use their masks correctly. I constantly see people touching and adjusting their masks and wearing them beneath their noses. And as others have said, the users seem to think the mask makes them immune and then break distancing rules as well.Masks are also not an excuse for people who have potential symptoms to go out - it's not a case of '...I have a persistent cough, but I can go out if I wear a mask...'.
When I went to the GP surgery on Thursday it was a very stressful experience. She wouldn't give me a video call so had to go in for a face to face appointment. When I had been in the summer to pick up a script you went in and out of open doors - no touching door handles etc. This time it was different - back to the usual of everyone in and out of the same door. I sat in the waiting room with social distancing and masks. One chap was coughing and blowing his nose and therefor had to keep taking his mask off. There were about ten people in and out for the one door not using any hand sanitizer, one young chap was in and out of the door three or four times, went outside took his mask off blew his nose and put the tissue back in his pocket and then put his mask back on and came back inside touching the door handles. After I had seen the doctor I went out said door and managed to open the push bar with my elbow then sanitized my hands before getting in the car. I would like to know how long the virus can stay on door handles etc that multiple people are using without being sanitized, not a good experience for me at all.
Those posters would be useful displayed in shops, public transport etc. @steveTu. I’d like to take an air horn round with me for the flouters and twits*.
That must have been unsettling @floralies. We can’t stop others being thoughtless (in my opinion, ‘coughers’ should stay outside and the waiting room should insist on 2M distance between people plus provide sanitiser) but if you gel hands and stay clear from people as much as you can, then you give yourself a chance.
It's funny how the whole conversation about covering one's face to protect everyone around you becomes such an emotional conversation when it is a simple matter of logical mitigation of a common threat. It's a practical way to help each other after the testing year we've had so far. And I'm sorry, but if you refuse to contribute for the common good we have every right to judge you. There's no free pass during a pandemic, your refusal to wear one puts others at risk. Frankly, it's good to see shops upholding a no mask no entry policy, if you can't wear one have someone who can to shop for you. Nice and simple. All this self certificated exception mess is not helping anyone.
@BenCotto in scientific terms that's very difficult to define, because it's a behavioral question that can't be tested via an experiment on the virus.
As an example: whether we are looking at aerosol or surface transmission, the virus is the same. If the virus reaches me through touch or breath, I become infected. If I don't touch an infected surface, I can't be infected. If I stay X distance / 500 feet from a carrier, I can't be infected by aerosol.
The virus is equally infectious as an aerosol droplet or as a droplet on a hard surface. Droplets remain suspended and infectious for 1 to 3 hours in air, or 24 to 72 hours on a surface.
So the question is actually more about individual behavior. Am I more likely to walk into a cloud of droplets, or touch a surface then touch my face. And just as importantly, are those aerosol droplets in an enclosed area or will they be dispersed by air movement etc.
There are studies in progress in China to try to identify the most common transmission mechanism in public transport, but again the challenge is definitively proving the source of infection.
What's fair to say is that, all things being equal, droplets in air in an enclosed space with no/low air flow are likely to result in a greater number of infections than other scenarios. That's the entire purpose of social distancing and limiting indoor contact. Quantifying it is significantly harder though, and surface contact is just as likely to result in infection onice the contact has been made.
Thanks for the link @chicky, exactly what I wanted to read.
It seems ridiculous of me to question WHO advice but I still don’t have clarity over the last batch of do’s.
If I don’t have the virus the mask serves almost no purpose but obviously must be worn because I do not know I do not have it.
If I do have the virus I can understand the advice about not touching the mask because I am sure it is impregnated with my infected exhalations. I touch the mask, my fingers touch a surface, others touch the same surface and the virus spreads. That make sense but if I do sneeze or have a drippy nose while wearing the mask I can’t see any solution.
My bigger problem comes with the advice about taking off the mask and storing it. If I already have the virus how are these measures helping me? I’m already infected. OK, it might marginally reduce the chances of me infecting those in my household bubble but as there’ll be zillions of interactions with them anyway being cautious with my mask seems to be of almost no benefit. Likewise the daily washing of the mask is of no help because I already have the virus. Maybe I don’t have the virus but others’ infected droplets have landed on it. Wouldn’t I have inhaled them long before it got to the end of the day and my mask went in the wash? Obviously I understand the benefits of good hygiene especially with something attached to my nose and mouth but I would like someone to explain to me how I am missing the point with the WHO advice.
Can a droplet stay suspended in air for 1-3 hours? Surely it would land on something. Can it get blown about in the wind and land somewhere far away if you're out in the park, for example? I suppose the droplets on surfaces would be less concentrated than if you, unmasked, coughed near someone. So a good enough reason to wear a mask and wash your hands.
Posts
Is there any research on this?
https://www.pnas.org/content/117/26/14857
After I had seen the doctor I went out said door and managed to open the push bar with my elbow then sanitized my hands before getting in the car.
I would like to know how long the virus can stay on door handles etc that multiple people are using without being sanitized, not a good experience for me at all.
That must have been unsettling @floralies. We can’t stop others being thoughtless (in my opinion, ‘coughers’ should stay outside and the waiting room should insist on 2M distance between people plus provide sanitiser) but if you gel hands and stay clear from people as much as you can, then you give yourself a chance.
*edited for politeness.
As an example: whether we are looking at aerosol or surface transmission, the virus is the same. If the virus reaches me through touch or breath, I become infected. If I don't touch an infected surface, I can't be infected. If I stay X distance / 500 feet from a carrier, I can't be infected by aerosol.
The virus is equally infectious as an aerosol droplet or as a droplet on a hard surface. Droplets remain suspended and infectious for 1 to 3 hours in air, or 24 to 72 hours on a surface.
So the question is actually more about individual behavior. Am I more likely to walk into a cloud of droplets, or touch a surface then touch my face. And just as importantly, are those aerosol droplets in an enclosed area or will they be dispersed by air movement etc.
There are studies in progress in China to try to identify the most common transmission mechanism in public transport, but again the challenge is definitively proving the source of infection.
What's fair to say is that, all things being equal, droplets in air in an enclosed space with no/low air flow are likely to result in a greater number of infections than other scenarios. That's the entire purpose of social distancing and limiting indoor contact. Quantifying it is significantly harder though, and surface contact is just as likely to result in infection onice the contact has been made.
It seems ridiculous of me to question WHO advice but I still don’t have clarity over the last batch of do’s.
If I don’t have the virus the mask serves almost no purpose but obviously must be worn because I do not know I do not have it.
If I do have the virus I can understand the advice about not touching the mask because I am sure it is impregnated with my infected exhalations. I touch the mask, my fingers touch a surface, others touch the same surface and the virus spreads. That make sense but if I do sneeze or have a drippy nose while wearing the mask I can’t see any solution.
My bigger problem comes with the advice about taking off the mask and storing it. If I already have the virus how are these measures helping me? I’m already infected. OK, it might marginally reduce the chances of me infecting those in my household bubble but as there’ll be zillions of interactions with them anyway being cautious with my mask seems to be of almost no benefit. Likewise the daily washing of the mask is of no help because I already have the virus. Maybe I don’t have the virus but others’ infected droplets have landed on it. Wouldn’t I have inhaled them long before it got to the end of the day and my mask went in the wash? Obviously I understand the benefits of good hygiene especially with something attached to my nose and mouth but I would like someone to explain to me how I am missing the point with the WHO advice.
Can it get blown about in the wind and land somewhere far away if you're out in the park, for example?
I suppose the droplets on surfaces would be less concentrated than if you, unmasked, coughed near someone. So a good enough reason to wear a mask and wash your hands.