Theoretically, wearing a mask can help reduce transmission in two ways:
Masks may reduce the amount of respiratory particles entering the environment through coughing, sneezing, speaking, and breathing by trapping them in the mask (‘source control’). Respiratory particles can contain the SARS-CoV-2 virus. Therefore, reducing the amount of particles emitted by people infected with SARS-CoV-2 may reduce exposure risks for healthy individuals. Since asymptomatic and pre-symptomatic individuals can still spread the SARS-CoV-2 virus, mask use by ‘healthy’ people (people without COVID-19 symptoms) may be important in reducing exposure risks to others.
Masks may offer some level of protection against personal exposure by preventing some respiratory particles from reaching your nose or mouth. The level of protection is dependent on the type of mask (or respirator) used (see this section for more info on mask types).
While both mechanisms may help prevent virus transmission, the primary benefit from the universal community-level use of masks is the reduction in the amount of SARS-CoV-2 entering the environment (‘source control’). See the below infographic which illustrates how masks may help reduce pathogen transmission via airborne particles.
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