Modelling airborne infection risk in urban environments

The transmission of airborne infection (e.g. SARS-CoV-2 virus) from expiratory activities is strongly influenced by the distance between people, types of expiratory activity, and ambient environmental conditions. Physical distancing is a long-term non-pharmaceutical intervention (NPI) to control and reduce (e.g. COVID-19) infection risk in the absence of a vaccine and adequate medical treatment. Normally the open outdoor environment is assumed to be safe with sufficient wind dilution. However, the risk is largely unknown for dense urban environments where the wind dilution capacity is significantly reduced, especially during outdoor crowded events such as public protests. The widely used 2-m physical distancing guideline is not sufficient to apply in dense urban environments where a tempo-spatial variability of various environmental variables (e.g. wind, air temperature and humidity) exist. Such dynamic outdoor environments will significantly change the dispersion, evaporation and eventual fate of expelled droplets in air, and therefore impact the physical distancing safety threshold. This PhD project aims to better understand how the infectious disease (e.g. COVID-19) is transmitted in urban environments using modeling approach, and help to determine the safe physical distancing threshold in the more realistic social contexts where people routinely interact.