Document Type
Article
Publication Date
1-25-2022
Abstract
The phase state of respiratory aerosols and droplets has been linked to the humidity-dependent survival of pathogens such as SARS-CoV-2. To inform strategies to mitigate the spread of infectious disease, it is thus necessary to understand the humidity-dependent phase changes associated with the particles in which pathogens are suspended. Here, we study phase changes of levitated aerosols and droplets composed of model respiratory compounds (salt and protein) and growth media (organic-inorganic mixtures commonly used in studies of pathogen survival) with decreasing relative humidity (RH). Efflorescence was suppressed in many particle compositions and thus unlikely to fully account for the humidity-dependent survival of viruses. Rather, we identify organic-based, semisolid phase states that form under equilibrium conditions at intermediate RH (45 to 80%). A higher-protein content causes particles to exist in a semisolid state under a wider range of RH conditions. Diffusion and, thus, disinfection kinetics are expected to be inhibited in these semisolid states. These observations suggest that organic-based, semisolid states are an important consideration to account for the recovery of virus viability at low RH observed in previous studies. We propose a mechanism in which the semisolid phase shields pathogens from inactivation by hindering the diffusion of solutes. This suggests that the exogenous lifetime of pathogens will depend, in part, on the organic composition of the carrier respiratory particle and thus its origin in the respiratory tract. Furthermore, this work highlights the importance of accounting for spatial heterogeneities and time-dependent changes in the properties of aerosols and droplets undergoing evaporation in studies of pathogen viability.
Identifier
PMID: 35064080
DOI
10.1073/pnas.2109750119
Publisher
National Academy of Sciences of the United States of America
ISSN
00278424
Repository Citation
Huynh, E., Olinger, A., Woolley, D., Kohli, R. K., Choczynski, J. M., Davies, J. F., Lin, K., ... & Davis, R. D. (2022). Evidence for a semisolid phase state of aerosols and droplets relevant to the airborne and surface survival of pathogens. Proceedings of the National Academy of Sciences of the United States of America, 119(4), Article e2109750119. https://doi.org/10.1073/pnas.2109750119
Publication Information
Proceedings of the National Academy of Sciences of the United States of America
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.