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One thing this crisis will have taught me is that many doctors, including those who work in academic medicine, are spectacularly dumb. https://www.nejm.org/doi/full/10.1056/NEJMp2006372">https://www.nejm.org/doi/full/...
Imagine being so stupid that you don& #39;t understand that, even if masks only lower the probability of infection a little bit at the individual-level, they could have a huge effect at the population-level by reducing the reproduction rate.
Of course, that& #39;s when you accept their premise, but you shouldn& #39;t. In the case of the flu, the relation between probability of infection and initial viral load is approximately linear at low doses, but sure masks that block ~80% of droplets don& #39;t work 
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They also block aerosols, though much less effectively except for N95/FFP2 respirators, but again even a bit of protection could matter a great deal at the population-level and there is evidence droplets play a larger role in transmission of COVID-19. https://medium.com/@Cancerwarrior/covid-19-why-we-should-all-wear-masks-there-is-new-scientific-rationale-280e08ceee71">https://medium.com/@Cancerwa...
