When people cough, sneeze, sing, talk, or breathe, they exhale water droplets from their respiratory system into the air. These water droplets can carry viral particles and may be breathed in by others in close proximity. Cloth masks can trap the exhaled droplets and prevent them, and their viral particles, in the mask. Masks are an important tool in slowing the spread, but masks alone are not 100% effective in preventing the spread of coronavirus. When used with other strategies, wearing a cloth face mask can help reduce the spread of disease.
Source: https://www.cdc.gov/coronavirus/2019-ncov/more/masking-science-sars-cov2.html
Swiss Cheese Model – Slow The Spread
Think of each coronavirus mitigation strategy as a slice of swiss cheese. Each one- handwashing, mask wearing, social distancing, disinfecting, and testing- has holes. They all offer some level of protection, but none are 100% effective in stopping coronavirus spread when used alone. When used together, those strategies provide multiple layers of protection. It is like stacking slices of swiss cheese. One slice has multiple holes, but as you stack slices, there are fewer and fewer holes through the block of cheese, which helps to slow the spread of the virus. Using multiple strategies will help fill the gaps, and better protect you and your loved ones.