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From a public policy perspective, shortages in supply for surgical face masks and N95 respirators, as well as concerns about their side effects and the discomfort of prolonged use ( 10), have led to public use of a variety of solutions that are generally less restrictive (such as homemade cotton masks or bandanas) but usually of unknown efficacy. Still, determining mask efficacy is a complex topic that is still an active field of research, made even more complicated because the infection pathways for COVID-19 are not yet fully understood and are complicated by many factors such as the route of transmission, correct fit and usage of masks, and environmental variables. Recent studies suggest that wearing face masks reduces the spread of COVID-19 on a population level and consequently blunts the growth of the epidemic curve ( 7, 8). The premise of protection from infected persons wearing a mask is simple: Wearing a face mask will reduce the spread of respiratory droplets containing viruses. This latter role has been embraced by multiple governments and regulatory agencies ( 5), since patients with COVID-19 can be asymptomatic but contagious for many days ( 6). The most common application in modern medicine is to provide protection to the wearer (e.g., first responders), but surgical face masks were originally introduced to protect surrounding persons from the wearer, such as protecting patients with open wounds against infectious agents from the surgical team ( 3) or the persons surrounding a tuberculosis patient from contracting the disease via airborne droplets ( 4). In general, the term “face mask” governs a wide range of protective equipment with the primary function of reducing the transmission of particles or droplets.