Airborne transmission occurs through droplet-mediated transport of viruses following the expulsion of an aerosol by an infected host. Transmission efficiency results from the interplay between virus survival in the drying droplet and droplet suspension time in the air, controlled by the coupling between water evaporation and droplet sedimentation. Furthermore, droplets are made of a respiratory fluid and thus, display a complex composition consisting of water and nonvolatile solutes. Here, we quantify the impact of this complex composition on the different phenomena underlying transmission. Solutes lead to a nonideal thermodynamic behavior, which sets an equilibrium droplet size that is independent of relative humidity. In contrast, solutes do not significantly hinder transport due to their low initial concentration. Realistic suspension times are computed and increase with increasing relative humidity or decreasing temperature. By uncoupling drying and suspended stages, we observe that enveloped viruses may remain infectious for hours in dried droplets. However, their infectivity decreases with increasing relative humidity or temperature after dozens of minutes. Examining expelled droplet size distributions in the light of these results leads to distinguishing two aerosols. Most droplets measure between 0 and 40 µm and compose an aerosol that remains suspended for hours. Its transmission efficiency is controlled by infectivity, which decreases with increasing humidity and temperature. Larger droplets form an aerosol that only remains suspended for minutes but corresponds to a much larger volume and thus, viral load. Its transmission efficiency is controlled by droplet suspension time, which decreases with increasing humidity and decreasing temperature.

Metalla-bis-dicarbollides, such as the cobalta-bisdicarbollide (COSAN) anion [Co(C 2 B 9 H 11) 2 ] À ,h ave attracted much attentioni nb iology but ad eep understanding of their interactions with cell components is stillm issing. For this purpose, we studied the interactions of COSANw ith the glucosem oiety,w hich is ubiquitous at biological interfaces. Octyl-glucopyranoside surfactant (C8G1) was chosena sa model as it self-assembles in water and creates ah ydrated glucose-covered interface. At low COSAN content and below the critical micellar concentration (CMC) of C8G1, COSAN binds to C8G1 monomers through the hydrophobic effect. Abovet he CMC of C8G1, COSAN adsorbs onto C8G1 micelles through the superchaotropic effect. At high COSAN concentrations, COSANd isrupts C8G1 micelles and the assemblies become similart oC OSAN micelles but with as mall amount of solubilized C8G1.T herefore, COSAN binds in a versatile way to C8G1 throughe ither the hydrophobic or superchaotropice ffect depending on their relative concentrations. Scheme1.Cobalt-bis-(dicarbollide) Co III [(C 2 B 9 H 11) 2 ] À (cis-rotamer;top)and octyl-glucopyranoside, C8G1(bottom).