Here we consider the upper limit, i.e. 3000 particles in 72 µm droplet (giving rise to 1010.18 virus copies per ml), as this produces larger clusters of virus and hence less penetrating through filters. Applying the drying kinetic model to droplet size distributions given by Han et al.(3), the resulting particle size distribution of the dried particles are predicted to be in the range 0.84-18 µm, as also shown in Figure 2.