By June 19, 2020, there had been 84940 COVID-19 confirmed cases in China, in which 83% of the clustered infections occurred within families. Thus, exploring the relative contributions of different transmission routes is significant for developing efficient intervention strategies in household. In this study, we build a mathematical model to quantify the relative degrees of importance of airborne, droplet and contact route in COVID-19 transmission in household environments. We find that the droplet and contact routes play the dominant role in COVID-19 transmission in household. Keeping a 1.5-2 m distance when communicating with the infector is the key intervention to control droplet transmission. Hand hygiene and surface cleaning are significant for controlling contact transmission. The infection risk by airborne route is relatively small, however, when the virus concentration in the droplets exhaled by the infector is high (possibly super-spreader), e. g. 107 mRNA copy/mL, the infection risk via the airborne route can be as high as 26%. This study may provide a theoretical guidance for developing targeted interventions in household environments.

SARS-CoV-2  /  droplet transmission  /  contact transmission  /  airborne transmission  /  relativeimportance  /  mathematical model