1
|
Longest AK, Rockey NC, Lakdawala SS, Marr LC. Review of factors affecting virus inactivation in aerosols and droplets. J R Soc Interface 2024; 21:18. [PMID: 38920060 DOI: 10.1098/rsif.2024.0018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Accepted: 04/25/2024] [Indexed: 06/27/2024] Open
Abstract
The inactivation of viruses in aerosol particles (aerosols) and droplets depends on many factors, but the precise mechanisms of inactivation are not known. The system involves complex physical and biochemical interactions. We reviewed the literature to establish current knowledge about these mechanisms and identify knowledge gaps. We identified 168 relevant papers and grouped results by the following factors: virus type and structure, aerosol or droplet size, temperature, relative humidity (RH) and evaporation, chemical composition of the aerosol or droplet, pH and atmospheric composition. These factors influence the dynamic microenvironment surrounding a virion and thus may affect its inactivation. Results indicate that viruses experience biphasic decay as the carrier aerosols or droplets undergo evaporation and equilibrate with the surrounding air, and their final physical state (liquid, semi-solid or solid) depends on RH. Virus stability, RH and temperature are interrelated, but the effects of RH are multifaceted and still not completely understood. Studies on the impact of pH and atmospheric composition on virus stability have raised new questions that require further exploration. The frequent practice of studying virus inactivation in large droplets and culture media may limit our understanding of inactivation mechanisms that are relevant for transmission, so we encourage the use of particles of physiologically relevant size and composition in future research.
Collapse
Affiliation(s)
- Alexandra K Longest
- Department of Civil and Environmental Engineering, Virginia Tech , Blacksburg, VA, USA
| | - Nicole C Rockey
- Department of Civil and Environmental Engineering, Duke University , Durham, NC, USA
| | - Seema S Lakdawala
- Department of Microbiology and Immunology, Emory University , Atlanta, GA, USA
| | - Linsey C Marr
- Department of Civil and Environmental Engineering, Virginia Tech , Blacksburg, VA, USA
| |
Collapse
|
2
|
Haddrell A, Oswin H, Otero-Fernandez M, Robinson JF, Cogan T, Alexander R, Mann JFS, Hill D, Finn A, Davidson AD, Reid JP. Ambient carbon dioxide concentration correlates with SARS-CoV-2 aerostability and infection risk. Nat Commun 2024; 15:3487. [PMID: 38664424 PMCID: PMC11045827 DOI: 10.1038/s41467-024-47777-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2023] [Accepted: 04/11/2024] [Indexed: 04/28/2024] Open
Abstract
An improved understanding of the underlying physicochemical properties of respiratory aerosol that influence viral infectivity may open new avenues to mitigate the transmission of respiratory diseases such as COVID-19. Previous studies have shown that an increase in the pH of respiratory aerosols following generation due to changes in the gas-particle partitioning of pH buffering bicarbonate ions and carbon dioxide is a significant factor in reducing SARS-CoV-2 infectivity. We show here that a significant increase in SARS-CoV-2 aerostability results from a moderate increase in the atmospheric carbon dioxide concentration (e.g. 800 ppm), an effect that is more marked than that observed for changes in relative humidity. We model the likelihood of COVID-19 transmission on the ambient concentration of CO2, concluding that even this moderate increase in CO2 concentration results in a significant increase in overall risk. These observations confirm the critical importance of ventilation and maintaining low CO2 concentrations in indoor environments for mitigating disease transmission. Moreover, the correlation of increased CO2 concentration with viral aerostability need to be better understood when considering the consequences of increases in ambient CO2 levels in our atmosphere.
Collapse
Affiliation(s)
- Allen Haddrell
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, UK.
| | - Henry Oswin
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, UK
| | | | - Joshua F Robinson
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Mainz, Germany
| | - Tristan Cogan
- Bristol Veterinary School, University of Bristol, Langford House, Langford, Bristol, UK
| | - Robert Alexander
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Jamie F S Mann
- Bristol Veterinary School, University of Bristol, Langford House, Langford, Bristol, UK
| | - Darryl Hill
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Adam Finn
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
- School of Population Health Sciences, University of Bristol, Bristol, UK
| | - Andrew D Davidson
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK.
| | - Jonathan P Reid
- School of Chemistry, Cantock's Close, University of Bristol, Bristol, UK.
| |
Collapse
|
3
|
Groth R, Niazi S, Oswin HP, Haddrell AE, Spann K, Morawska L, Ristovski Z. Toward Standardized Aerovirology: A Critical Review of Existing Results and Methodologies. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:3595-3608. [PMID: 38355395 DOI: 10.1021/acs.est.3c07275] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/16/2024]
Abstract
Understanding the airborne survival of viruses is important for public health and epidemiological modeling and potentially to develop mitigation strategies to minimize the transmission of airborne pathogens. Laboratory experiments typically involve investigating the effects of environmental parameters on the viability or infectivity of a target airborne virus. However, conflicting results among studies are common. Herein, the results of 34 aerovirology studies were compared to identify links between environmental and compositional effects on the viability of airborne viruses. While the specific experimental apparatus was not a factor in variability between reported results, it was determined that the experimental procedure was a major factor that contributed to discrepancies in results. The most significant contributor to variability between studies was poorly defined initial viable virus concentration in the aerosol phase, causing many studies to not measure the rapid inactivation, which occurs quickly after particle generation, leading to conflicting results. Consistently, studies that measured their reference airborne viability minutes after aerosolization reported higher viability at subsequent times, which indicates that there is an initial loss of viability which is not captured in these studies. The composition of the particles which carry the viruses was also found to be important in the viability of airborne viruses; however, the mechanisms for this effect are unknown. Temperature was found to be important for aerosol-phase viability, but there is a lack of experiments that directly compare the effects of temperature in the aerosol phase and the bulk phase. There is a need for repeated measurements between different research groups under identical conditions both to assess the degree of variability between studies and also to attempt to better understand already published data. Lack of experimental standardization has hindered the ability to quantify the differences between studies, for which we provide recommendations for future studies. These recommendations are as follows: measuring the reference airborne viability using the "direct method"; use equipment which maximizes time resolution; quantify all losses appropriately; perform, at least, a 5- and 10-min sample, if possible; report clearly the composition of the virus suspension; measure the composition of the gas throughout the experiment. Implementing these recommendations will address the most significant oversights in the existing literature and produce data which can more easily be quantitatively compared.
Collapse
Affiliation(s)
- Robert Groth
- School of Earth and Atmospheric Sciences, International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland 4000, Australia
| | - Sadegh Niazi
- School of Earth and Atmospheric Sciences, International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland 4000, Australia
| | - Henry P Oswin
- School of Earth and Atmospheric Sciences, International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland 4000, Australia
| | - Allen E Haddrell
- School of Chemistry, Cantock's Close, University of Bristol, Bristol BS8 1TS, United Kingdom
| | - Kirsten Spann
- School of Biomedical Sciences, Centre for Immunology and Infection Control, Queensland University of Technology, Brisbane, Queensland 4000, Australia
| | - Lidia Morawska
- School of Earth and Atmospheric Sciences, International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland 4000, Australia
| | - Zoran Ristovski
- School of Earth and Atmospheric Sciences, International Laboratory for Air Quality and Health, Queensland University of Technology, Brisbane, Queensland 4000, Australia
| |
Collapse
|
4
|
Oswin HP, Blake E, Haddrell AE, Finn A, Sriskandan S, Reid JP, Halliday A, Goenka A. An assessment of the airborne longevity of group A Streptococcus. MICROBIOLOGY (READING, ENGLAND) 2024; 170:001421. [PMID: 38180461 PMCID: PMC10866022 DOI: 10.1099/mic.0.001421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/06/2023] [Accepted: 12/08/2023] [Indexed: 01/06/2024]
Abstract
Group A streptococcus (GAS) infections result in more than 500 000 deaths annually. Despite mounting evidence for airborne transmission of GAS, little is known about its stability in aerosol. Measurements of GAS airborne stability were carried out using the Controlled Electrodynamic Levitation and Extraction of Bioaerosols onto a Substrate (CELEBS) instrument. CELEBS measurements with two different isolates of GAS suggest that it is aerostable, with approximately 70 % of bacteria remaining viable after 20 min of levitation at 50 % relative humidity (RH), with lower survival as RH was reduced. GAS airborne viability loss was driven primarily by desiccation and efflorescence (i.e. salt crystallization), with high pH also potentially playing a role, given reduced survival in bicarbonate containing droplet compositions. At low enough RH for efflorescence to occur, a greater proportion of organic components in the droplet appeared to protect the bacteria from efflorescence. These first insights into the aerosol stability of GAS indicate that airborne transmission of these respiratory tract bacteria may occur, and that both the composition of the droplet containing the bacteria, and the RH of the air affect the duration of bacterial survival in this environment. Future studies will explore a broader range of droplet and air compositions and include a larger selection of GAS strains.
Collapse
Affiliation(s)
- Henry P. Oswin
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol, UK
| | - Evie Blake
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Allen E. Haddrell
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol, UK
| | - Adam Finn
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
- Paediatric Immunology and Infectious Diseases, Bristol Royal Hospital for Children, Bristol, UK
| | - Shiranee Sriskandan
- NIHR Health Protection Research Unit in Healthcare-associated Infection and Antimicrobial Resistance, Imperial College London, London, UK
- Centre for Bacterial Resistance Biology, Imperial College London, London, UK
| | - Jonathan P. Reid
- School of Chemistry, University of Bristol, Cantock’s Close, Bristol, UK
| | - Alice Halliday
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Anu Goenka
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
- Paediatric Immunology and Infectious Diseases, Bristol Royal Hospital for Children, Bristol, UK
| |
Collapse
|
5
|
Groth R, Niazi S, Spann K, Johnson GR, Ristovski Z. Physicochemical characterization of porcine respiratory aerosol and considerations for future aerovirology. PNAS NEXUS 2023; 2:pgad087. [PMID: 37007717 PMCID: PMC10063220 DOI: 10.1093/pnasnexus/pgad087] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 03/08/2023] [Indexed: 06/19/2023]
Abstract
Understanding the mechanisms which inactivate airborne viruses is a current challenge. The composition of human respiratory aerosol is poorly understood and needs to be adequately investigated for use in aerovirology studies. Here, the physicochemical properties of porcine respiratory fluid (PRF) from the trachea and lungs were investigated both in bulk solutions and in aerosols. The mass ratio of Na:K in PRF compared with cell culture media (Dulbecco's Modified Eagle Medium, DMEM), which is frequently used in aerovirology studies, was significantly lower (∼2:1 vs ∼16:1). PRF contained significantly more potassium and protein than DMEM. PRF aerosols of all samples were similarly hygroscopic to human respiratory aerosol. PRF particles could nucleate with spatially separated crystals, indicating that the protein matrix was sufficiently viscous to prevent the complete coalescence of aqueous salts prior to efflorescence. The effects of these differences in compositions on the viability of viruses are currently not well understood. The virus suspensions in aerovirology studies need to be reconsidered to adequately reflect a real-world expiration scenario.
Collapse
Affiliation(s)
- Robert Groth
- School of Earth and Atmospheric Sciences, International Laboratory for Air Quality and Health, Faculty of Science, Queensland University of Technology, Brisbane, QLD 4000, Australia
| | - Sadegh Niazi
- School of Earth and Atmospheric Sciences, International Laboratory for Air Quality and Health, Faculty of Science, Queensland University of Technology, Brisbane, QLD 4000, Australia
| | - Kirsten Spann
- School of Biomedical Sciences, Centre for Immunology and Infection Control, Faculty of Health, Queensland University of Technology, Brisbane, QLD 4000, Australia
| | - Graham R Johnson
- School of Earth and Atmospheric Sciences, International Laboratory for Air Quality and Health, Faculty of Science, Queensland University of Technology, Brisbane, QLD 4000, Australia
| | | |
Collapse
|