Risk assessment of respiratory droplet infections caused by coughing in various indoor dynamic environments

Since most respiratory infections occur in confined spaces, it is necessary to further investigate the effect of wake caused by human movement on droplet dispersion. This paper investigates the effects of droplet dispersion in dynamic indoor environment by using computational fluid dynamics when the infected person remained stationary, and the susceptible person moved at different speeds and at different distances from the infected person. The modified Wells-Riley model, which introduced the concept of local quantum concentration, was used to estimate the transient infection probability of a virtual person inhaling droplets at 1 m distance from an infected person. The results show that the human motion speed has a stronger effect on the diffusion of 1 μm droplets. The distance between people had a more significant effect on the resuspension and diffusion of 34 μm droplets. The effect of both is very small for droplets above 67 μm. The higher human movement speed results in much higher probability of infection within 40 s–55 s, and has the highest probability about 96.2 × 10−6. The distance between people mainly affects the probability of infection at the beginning of the cough (10s). When the distance is 0.1 m, the infection probability is highest at 10 s with a value of 232.1 × 10−6. In addition, it was found that when one person passes another, a distance of at least 1 m is maintained between them. In this paper, this study provides greater insight into the impact of human activities on infection risk in indoor environments.