Abstract

Throughout human history, nothing has killed more people than infectious diseases. Natural pandemics are ever-present and the next pandemic is a matter of ‘when’, not ‘if’. The event frequency for pandemics caused by natural and synthetic pathogens are likely to increase due to human encroachment into natural environments, bio-terrorism threats, high population density urban settings, lifestyles, and global connectivity. Covid-19 caught us unprepared, and we ended up responding too late; nevertheless, in the last couple of years, we have made great strides in our understanding of the mechanism of airborne disease transmission and its control. To a considerable extent, airborne disease transmission is a fluid dynamics problem—the formation of droplets and aerosols are interfacial problems, and their transport and consequently the transmission is a building ventilation flow problem. The talk is divided into two parts: In the first part, I will briefly discuss the advances I have made in the field of interfacial flows. I have discovered processes of fundamental importance which have previously been unrecognised and which challenges the textbook understanding of these flows. Subsequently, I will briefly discuss the challenges associated with the ventilation flow problem and some of the key advances made in the field. And finally, I will summarise the outstanding questions—the known unknowns—that emerged from our work during the pandemic, which need to be addressed.