I got into a bit of a debate earlier today whether COVID was transmissible via the air.
The argument seemed to come down to definitions.
Of course the virus leaves a person when they breathe. So, it is in the air.
My understanding was airborne transmission means it can float in the air and pass through air ducts and linger in the air for a long time and infect anyone who breathes it in.
That is opposed to someone three feet away who breathes in what you are exhaling or what you exhale drops to a surface and someone touches it and then wipes their eye and infects theirself.
Do we know? Is someone in my building able to infect me from several floors away because the virus is floating through all the air ducts?
It seems to be far, far more transmitted by droplet rather than airborne, though there is some evidence that some folks may have been infected from exposure from covid carriers more than 6 feet away, which would mean that yes, it can be transmitted in the airborne manner.
But most covid infections by far seem to stem from droplet exposure.
More study is needed.
I don’t worry too much about airborne transmission in my practice, but I do wear my mask 99% of the time at work.
ISTM that the distinction between “droplet” and “airborne” is rather academic since the infectious agent, as noted above, is in droplets that remain suspended in the air for potentially a long time, and hence pass the infection through air currents. This is distinct from, for example, getting the infection from touching infected surfaces, which may or may not be a significant source of infection. I’ve also read that eating when your hands may be infected is an unlikely pathway for infection because the virus will likely not survive digestive processing. Still, I always scrupulously wash my hands when I return from being out of the house, and keep a mini bottle of Purell in the car.
Morawska had spent more than two decades advising a different branch of the WHO on the impacts of air pollution. When it came to flecks of soot and ash belched out by smokestacks and tailpipes, the organization readily accepted the physics she was describing—that particles of many sizes can hang aloft, travel far, and be inhaled. Now, though, the WHO’s advisers seemed to be saying those same laws didn’t apply to virus-laced respiratory particles. To them, the word airborne only applied to particles smaller than 5 microns. Trapped in their group-specific jargon, the two camps on Zoom literally couldn’t understand one another.
Most of the air I expel when breathing with a mask on poofs out the sides of the mask (as my foggy glasses can attest to). Likewise, the air I breathe in is largely coming in from around the edges. And, more to the point, the disease will come in through the air ducts in my building (I live in a hi-rise). So, even at home I am at risk?
And, perhaps most importantly, how is it planes are still allowed to fly and carry passengers? A closed tube with people shoulder to shoulder and aerosol transmission? Talk about a super-spreader machine.
The WHO really dragged its feet in calling the virus airborne. It was obvious a long time before that. Nursing homes were seeing patients infected who never came within 50 feet of an infected person. An early outbreak in a restaurant had a number of people get sick who were way downstream from A/C blowing past from an infected person.
It also seems clear that the virus survives in the air longer if it’s colder, which is why meat packing plants were super-spreaders and air conditioning has been implicated. One study put a bunch of cantaminated products in refrigerators, and it was found that three weeks later, 100% of the virus was still alive if the temp was below 4C.
And yet, none of this information seems to be informing the public health debate. For example, we still focus on useless cloth masks, while ignoring ventilation improvements and airflow control.
Masks can be very effective if they fit right, filter well, and are worn properly. Air should not be going around your mask, incoming or outgoing. Fogging glasses does not necessarily mean the mask is leaking.
Quite a while back experts started saying people needed to upgrade to better masks now that they are widely available. A good, well-fitted N95 equivalent mask will filter at least 95% (and some up to 98-99%) of 0.3 micron particles from passing through.
Experts have also been saying for a long time now that we should be focusing more on HVAC systems than on things like wiping surfaces and keeping 6 feet apart. You should be concerned if your home is served by an HVAC system that doesn’t adequately filter the air, and is mixing air from multiple units.
The mask pictured below is ubiquitous. It does not fit tightly, air goes around it with ease. It fogs glasses.
Yet, these are often used by surgeons. So…I dunno. Will N95 masks protect me and others more? How much better? So much that N95 should be mandated?
My understanding is the mask below stops the person wearing it from spewing water vapor droplets out into the environment and not really protect them form inhaling the virus. But, if the virus is airborne and just floats around then do these masks really help?
(Really asking…FTR I wear a mask when out of my home. I am not a maskhole. Also fully vaccinated with booster.)
You may notice that I said cloth masks. Details matter.
N95 masks are 90-95% effective in stopping the virus from getting out or in, if worn correctly.
Surgical masks are maybe 50% effective at stopping droplets containing the virus from getting in and out, but they are often poorly fitted and the air simply escapes around the side.
Cloth masks range from almost useless to completely useless, depending on the weave.
And yet, we treat them all the same. You can even comply with a mask mandate by pulling a knitted wool scarf over your kouth and nose, and you can see through those.
At the same time, you can go into indoor spaces where no effort at all has been made to improve air ventilation, or even check it to make sure there aren’t large stagnant spots where the virus can accumulate.
Yes, if you take a tight-weave cloth, fold it into three layers as WebMD suggests, then tightly affix it to your face with straps instead of ear loops, it might do some good. Not much, but better than nothing.
Now do the same with a loose-fitting cloth mask made out of random cloth attached with ear loops leaving gaps in the sides of your face. As I said, it might do a little good when sneezing pr coughing, catching the largest drops, but likely won’t do much for the general miasma in the air.
Here’s a tweet thread from Dr. Richard Corsi, environmental engineer and Dean of Engineering at UC Davis. He’s been banging on about the importance of filtration and air cleaning over hand sanitizer and deep cleaning almost since this began.
I’ve built one of his air purifiers (Corsi-Rosenthal box), using a box fan and furnace filters, and keep it in my cubicle at the office (which is maskless ).
Yeah, those masks, with nothing more, are between 50 and 70% effective. Way less than an N95, but way better than nothing.
I think higher risk environments should probably mandate N95/KN95/KF94/FFP2. So public transportation, large gatherings, people in high risk jobs, settings like that. But even just giving clearer advice to people about it would be good.
No, masks are for protecting others and ourselves. This was a piece of misinformation from early on when they were revering themselves on the whole mask thing.
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