“…The "New Coronavirus Pneumonia Diagnosis and Treatment Plan (Trial Version 7)" pointed out that the main route of SARS-CoV-2 transmission includes respiratory droplet transmission and close contracting transmission ( General Office of the National Health Commission, 2020 ; Jin et al, 2021 ). Significantly, there are many studies that provide strong evidence for airborne transmission of SARS-CoV-2 ( Robotto et al, 2021 ; Noorimotlagh et al, 2021 ; Stern et al, 2021 ; Baboli et al, 2021 ; Allen & Marr, 2020 ; Morawska et al, 2020 ). The transmission of virus-carrying droplets in the public bus is a dynamic process, and the suspension, deposition and escape of droplets are unsteady, leading to a change in the infection risk for passengers over time.…”