The idea that aerosol transmission of COVID is very important is gaining traction. Some scientists are even speculating that it’s the most important vector, especially for super-spreader events. The lady who infected 27 people in a Starbucks in Seoul by just sitting under the aircon for 2 hours seems to be a very clear case of massive aerosol spread. WHO and CDC are not on board yet, but they seem to be generally slow to adopt new ideas. Japan has been onboard from way back with the 3Cs but didn’t really do anything to convince the world about it.
The conventional wisdom on aerosol transmission seems to stem from an old book on the transmission of diseases but there is no basis for believing that only a highly infectious disease like measles can spread this way.
This FAQ has been put together by a bunch of researchers and provides advice and good justifications for all the advice. In particular the sections on general protection and on masks are well worth reading. They justify everything with references, they are clear on what’s still unknown and they debunk a bunch of misconceptions. Key points are summarized below.
They have also made a truly awful acronym to help you remember. It’s Avoid Crowding, Indoors, low Ventilation, Close proximity, long Duration, Unmasked, Talking/singing/Yelling/breathing hard (“A CIViC DUTY”).
Just remember that an infected person, breathing in an unventilated room can fill that room with floating virus, possibly for hours after they leave. And there are a bunch of fairly obvious factors that make you more or less likely to get infected:
- how many sources there are (more people => more chances of an infected person)
- filtering (their mask and your mask)
- how close you are to the source
- how much aerosol the source is producing (from normal breathing to screaming)
- ventilation (how often is the air replaced by clean air)
- how long you’re exposed
A tight fitting mask, even a cloth mask protects you and others (great news, if aerosols really are a big factor your mask really protects you now too, not just everyone else, maybe now even selfish pricks can wear a mask). You want multiple layers of cloth and don’t worry about “the virus is much smaller than the holes in your mask” that is not how aerosol filtering works. Your mask is not going to be perfect but it’s like sunburn, factor 50 is way better than factor 10 which is still better than nothing.
There’s lots more detail in the doc it’s worth reading those sections in full.
If you were being careful, a lot of the above is stuff you were doing anyway. However, people and places that take very visible precautions against droplets but do nothing for aerosols are potentially making things more dangerous by giving the impression of safety and encouraging people to expose themselves to more danger.
No comments:
Post a Comment