N95 masks do less than you think. Viral load matters.

Viral load matters.   Social-distancing and masks aren't absolutes, for crying out loud.  They cut back the number of copies you receive of the COVID-19 bat flu virus.   After four months, here finally is something that recognizes degrees of threat instead of absolutes.  Astonishingly, the authour had to piece together the evidence from older sources and common sense instead of from shiny new research.  The topic has been ignored in the press and not touted by experts with mikes.  We need better data.

Initial viral load seems likely to have a large impact on severity of Covid-19 infection. If we believe this, we should take this seriously, and evaluate both general policy and personal behavior differently in light of this information. We should also do our best to confirm or deny this hypothesis as soon as possible.

The failure to collect more and better information about Covid-19 has been atrocious, shameful, expensive and deadly.

What can those masks do?  Less than you imagine.  The bat virus is about 125 billionths of a meter across.  The highest-rated hospital-grade N95 masks stop 95% of  the particles that are 300 billionths of an inch across.  And only if properly fitted.  In other words, you can expect about one in twenty to get through.  Those virus copies mostly aren't floating around like little no-seeums on their own but are in much larger water droplets breathed, sneezed and coughed, about 3000 droplets per cough.   A realistic goal of a mask is to stop fine spray getting up your nose. to reduce incoming viral load.  And to protect others from the same, but then you shouldn't be that close to them in the first place.       If the virus you fear is in your neighbourhood, you'll probably pick up some copies.  That's with or without social distancing and with or without a mask.  But you can reduce the viral load.

Light load of wind (virus)

More from the article:

Mostly we’re not collecting any data at all that isn’t massively biased.
The more I think about the Covid-19 situation, the more I think the highest leverage thing most people reading this can do is to find ways to get our hands on better data.

Heavy load of wind (virus)