Respiratory infectious diseases can cause public health emergencies, threatening human well-being, social operation, and economic development. Clarifying the transmission mechanism of respiratory infectious diseases is essential for control measures. We review the main research findings on the transmission mechanism of respiratory infectious diseases in recent decades. The source characteristics of respiratory infectious diseases, the airborne transmission mechanism, the exposure of susceptible persons, and the infection risk assessment methods are discussed. Given that the dynamic scenario of respiratory infectious disease transmission has attracted wide attention in recent years, we summarize the effects of human movement on indoor airflow, pathogen diffusion, and human exposure. Considering the everyday use of facemasks, the effects of facemasks on source characteristics and infection risk are also discussed. Finally, future research prospects are proposed. The transmission mechanism of infectious diseases can be comprehensively explored by delving into patients' pathological characteristics and personnel protection measures. This exploration can be facilitated by establishing a multi-pose manikin database, enabling personalized and refined evaluations. Interdisciplinary cooperation will play a pivotal role in fostering a holistic understanding. Furthermore, it is crucial to account for the impact of individuals' activity patterns on disease transmission dynamics. This review is expected to reference public health emergency management.

To enhance the quantitative risk assessment method for domino accidents, this study investigated the synergistic impact between the wind and the physical effects (thermal radiation, toxic gas leakage) of different types of accidents. The mechanism of the synergistic effect was analyzed using empirical models. The synergistic situation between fire and toxic gas leakage was simulated using an experiment device model in computational fluid dynamics (CFD) software. The simulation results revealed that the synergistic effect could amplify the accident consequence severity. A hazardous chemical warehouse was taken as a case study for quantitative risk assessment. It was found that the synergistic effect would significantly amplify the individual risk, while the wind could either amplify or inhibit the risk, depending on the specific situation. The result indicates that the synergistic physical effects should be considered in the quantitative risk assessment of domino accidents. This research can serve as an important reference for improving the accuracy of the quantitative risk assessment for domino accidents.

Droplet transmission and aerosol transmission are both possible transmission pathways for many respiratory infections (e.g., COVID-19) and human movements may affect these viral particle transmission pathways. Realistic 3-D human models were used here in a computational fluid dynamics (CFD) study to analyze the effect of human movements on the transmission of virus particles exhaled by a patient. The changes in the airflow, pressure and particle diffusion were compared with experimental data to verify the accuracy of the computations. The results show that when a person passes by a sitting patient in a poorly ventilated room, the wake velocities can reach 1.6~2.0 m/s. The airflow velocity can reach 0.53 m/s at 0.10 m from the moving person, 0.22 m/s at 0.25 m away, and 0.13 m/s at 0.55 m away. The airflow fluctuations can last more than 10 s. Double peak airflow velocities are found near the moving person. The pressure difference of 0.49 Pa caused by the moving person moves the air and the viral particles into the wake of the moving person and slows the nearby droplet deposition. More than 50% of the viral particles are deposited on the moving person's body or spread further. Thus, this study recommends less cross-area movement in epidemic areas and that all people should wear masks and use personalized ventilation equipment.

High-quality measurements of the flow structures induced by human movements are important for analyzing indoor air quality. This study measures the longitudinal and cross-sectional velocity and vortex fields behind the moving body, and investigates the effect of movement and body-shape on a wake flow structure. Experiments were conducted in a small-scale chamber with a moving human-shaped manikin, measured by the particle image velocimetry technique. The dynamic changes of the movement-induced wake flow were compared both in different times and movement stages. A strong downward airflow and an upward vortex were observed following the moving body. The measurements also revealed symmetric downward and expansive vortices in the wake flow. During the movement, a longitudinal recirculation region can be predicted around the manikin. Compared with a moving cylinder, this study shows that the specific shape of the legs exerts an obvious impact on the flow behind the lower limbs. In particular, a horizontal flow was observed penetrating from between the legs, with a velocity of 0.5 m/s, which was equal to the moving speed of the manikin. Meanwhile, a computational fluid dynamic model was also employed to simulate the unsteady instantaneous flow affected by the human movement. The numerical results can reveal different stages of the wake generation, development, and decay in detail during the movement. By quantitatively comparing with the experimental data, the LES method has rendered a good alignment with the experimental result, not only in the velocity magnitude value but also in fluctuating quantity.