The source is for the "if not majority" part of that sentence. The other part is just me making an admittedly unsubstantiated claim.
https://www.nytimes.com/2020/07/04/health/239-experts-with-o...
> I know somehow on HN linking to a paper is seen as a mic-drop, but that is not the case in the real world.
Sure, but this is HN. You often have to source stuff just to not get downvoted.
"The evidence is admittedly incomplete for all the steps in COVID-19 microdroplet transmission, but it is similarly incomplete for the large droplet and fomite modes of transmission. The airborne transmission mechanism operates in parallel with the large droplet and fomite routes [16] that are now the basis of guidance."
By using arbitrarily high standards for evidence, I might as well claim there's no evidence that COVID is transmitted by large droplets or by smear infection. Where's the randomized trial that proves beyond any doubt that coughing in each other's faces will spread COVID?
I'm kind of surprised that there isn't much of a discussion about that, because if it is indeed a significant route (say 30%), all the masks and distancing in the world won't help until this is also addressed.