Glassy aerosol may promote virus transmission

The impact of respiratory particle composition on the equilibrium morphology and phase are not well understood. Furthermore, the effects of these different phases and morphologies on the viability of viruses embedded within these particles are equally unknown. Physiologically relevant respiratory fluid analogues were constructed, and their hygroscopic behavior were measured using an ensemble technique. A relationship between hygroscopicity and protein concentration was determined, providing additional validation to the high protein content of respiratory aerosol measured in prior works (>90%). Atomic force microscopy was used to probe the viscoelasticity of deposited protein particles, and transmission electron microscopy was used to observe the morphology of dried composite protein/salt particles. It was found that dried protein particles at indoor-relevant climatic conditions could exist separately in a glassy or viscous semisolid state. A glassy protein shell could kinetically ‘freeze’ a particle at conditions more favorable for virus viability.