Thread by @MackayIM

@TerryLerona @R_H_Ebright @nicolamlow @SCMPgraphics @mugecevik @profhelenward @jameschau TH answer lies in *how* the virus is propelled from an infected person.
Viruses are encased in mucous/snot (protein, salts+virus etc) which protect the virus. This case makes the droplets & smaller floaty droplet nuclei mostly much *larger* than the minimum pore size of the N95

@TerryLerona @R_H_Ebright @nicolamlow @SCMPgraphics @mugecevik @profhelenward @jameschau Naked virions - no snot protection - don't last very long at all in light and heat and air because they need their own thin lipid envelope *not* to dessicate.

@TerryLerona @R_H_Ebright @nicolamlow @SCMPgraphics @mugecevik @profhelenward @jameschau This seems to be a fundamental misunderstanding among those looking just at mask pore size.
Yes some virions are smaller than the pores, but the risk is more around propelled virus-laden *droplets*, not naked virions.

@TerryLerona @R_H_Ebright @nicolamlow @SCMPgraphics @mugecevik @profhelenward @jameschau The risk of getting an infectious dose (enough to start an infection) from unprotected virions is may be just too low to consider as a transmission route of much significance.

@TerryLerona @R_H_Ebright @nicolamlow @SCMPgraphics @mugecevik @profhelenward @jameschau When N95s (caveat-there are a range of makes & models) have been tested with actual viruses (eg flu at 120nm & even rhinoviruses at teensy 30nm, or 0.03 micrometers, across), & found to prevent passage of >95% of virus
😷ncbi.nlm.nih.gov/pmc/articles/P…
😷pubmed.ncbi.nlm.nih.gov/23571366-chall…

@TerryLerona @R_H_Ebright @nicolamlow @SCMPgraphics @mugecevik @profhelenward @jameschau But masks need to be used with care. They can *concentrate* viruses on their outside surfec through breathing in an an environment with lots of virus-laden droplets. If you touch that & then your face you may infect yourself. If they don't fit properly, they will leak.