Transmission risk of viruses in large mucosalivary droplets on the surface of objects: A time-based analysis

•Larger droplets contain more viruses and pose a greater risk of transmission than smaller ones.•Virus concentration changes after the exhaled droplets settle to the ground or on the surfaces of objects.•The risk of media transmission becomes low or even insignificant after a few days or even just a few hours.•Prevention of SARS-CoV-2 transmission through contaminated surfaces should be considered at according to time elapsed.