Are masks effective against coronavirus?

Unchallenged

A 2013 study found that surgical masks are somewhat effective at reducing exposure to the flu virus

Live influenza virus was measurable from the air behind all surgical masks tested. The data indicate that a surgical mask will reduce exposure to aerosolised infectious influenza virus; reductions ranged from 1.1- to 55-fold (average 6-fold), depending on the design of the mask.

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