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Evidence for a semisolid phase state of aerosols and droplets relevant to the airborne and surface survival of pathogens.
Huynh, Erik; Olinger, Anna; Woolley, David; Kohli, Ravleen Kaur; Choczynski, Jack M; Davies, James F; Lin, Kaisen; Marr, Linsey C; Davis, Ryan D.
  • Huynh E; Department of Chemistry, Trinity University, San Antonio, TX 78212.
  • Olinger A; Department of Chemistry, Trinity University, San Antonio, TX 78212.
  • Woolley D; Department of Chemistry, Trinity University, San Antonio, TX 78212.
  • Kohli RK; Department of Chemistry, University of California, Riverside, CA 92521.
  • Choczynski JM; Department of Chemistry, University of California, Riverside, CA 92521.
  • Davies JF; Department of Chemistry, University of California, Riverside, CA 92521.
  • Lin K; Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061.
  • Marr LC; Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA 24061.
  • Davis RD; Department of Chemistry, Trinity University, San Antonio, TX 78212; rdavis5@trinity.edu.
Proc Natl Acad Sci U S A ; 119(4)2022 01 25.
Article in English | MEDLINE | ID: covidwho-1642082
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.
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Full text: Available Collection: International databases Database: MEDLINE Main subject: Calcium Chloride / Serum Albumin / Sodium Chloride / SARS-CoV-2 / Respiratory Aerosols and Droplets / Models, Chemical Type of study: Observational study / Prognostic study Limits: Humans Language: English Year: 2022 Document Type: Article

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Full text: Available Collection: International databases Database: MEDLINE Main subject: Calcium Chloride / Serum Albumin / Sodium Chloride / SARS-CoV-2 / Respiratory Aerosols and Droplets / Models, Chemical Type of study: Observational study / Prognostic study Limits: Humans Language: English Year: 2022 Document Type: Article