In a hard time, when the number of Covid-19 cases is growing at the record speed, the fluid mechanics scientists are facing challenges on understanding of how the mucus droplets are formed, how the copies of virus are reproduced in expelling droplets, and how these droplets are driven by the flow. This will certainly help us to curb the spread of contagious droplets.

The objective of our zoom-meeting was to present the most relevant results in these studies. On the one hand the invited speakers - remarkable experts in fluid mechanics working on the COVID 19 Flow Physics - highlighted the essential knowledge on the dynamics of air-born transmissions from experience accumulated in the last century. On the other hand, they provided detailed explanations of recent studies over the last year. Thereby the specific emphasis was put on numerical simulations of the formation and dynamics of respiratory sprays. The most intriguing aspect of this zoom-meeting, put clearly in evidence by all speakers, was that a very large variety of questions remain open on the multiscale physics of air-born transmission. The zoom-meeting was joined by 320 participants over all the world.

The program included the following invited talks:

Direct and indirect Host-to-Host Airborne Contagion by Professor Alfredo Soldati (Institute of Fluid Mechanics and Heat Transfer, TU Wien)and Professor Francesco Picano (Dpt of Industrial Engineering, University of Padova, Padova);

On atomization process of human cough and sneezing by Professor Stephane Zaleski (Sorbonne University, Institut ∂'Alembert);

COVID-19 airborne transmission physics by Professor Rajat Mittal (Dpt of Mechanical Engineering, Johns Hopkins University);

Investigation of the flow-mask interaction: a simple model development by Senior Scientist Christophe Josserand (LadHyX, CNRS & Ecole Polytechnique);

High Fidelity Simulation of COVID-19 transmission through droplets and aerosols in realistic conditions by Professor Yves DUBIEF (Dpt of Mechanical Engineering, University of Vermont) in collaboration with LEGI (Grenoble), CORIA (Rouen), IMAG (Montpellier) and Safran Tech (Magny-Les-Hameaux).

The program included also the information on the ongoing project: Development of a software "plug-in" on CFD simulations of droplet emission and spreading for the design of work or transport environments" by Professor Lorenzo Botto (Process and Energy Dept., Delft University of Technology).