Differences in airborne stability of SARS-CoV-2 variants of concern is impacted by alkalinity of surrogates of respiratory aerosol

Allen E Haddrell; Mara Otero-Fernandez; Henry Oswin; Tristan A Cogan; James Bazire; Jiang-han Tian; Robert W Alexander; Jamie F S Mann; Darryl J Hill; Adam H R Finn; Andrew D Davidson; Jonathan P Reid

doi:10.1098/rsif.2023.0062

Differences in airborne stability of SARS-CoV-2 variants of concern is impacted by alkalinity of surrogates of respiratory aerosol

Allen E Haddrell
, Mara Otero-Fernandez
, Henry Oswin
, Tristan A Cogan
, James Bazire
, Jiang-han Tian
, Robert W Alexander
, Jamie F S Mann
, Darryl J Hill
, Adam H R Finn
, Andrew D Davidson
, Jonathan P Reid

Research output: Contribution to journal › Article (Academic Journal) › peer-review

34 Citations (Scopus)

141 Downloads (Pure)

Abstract

The mechanistic factors hypothesized to be key drivers for the loss of infectivity of viruses in the aerosol phase often remain speculative. Using a next-generation bioaerosol technology, we report measurements of the aero-stability of several SARS-CoV-2 variants of concern in aerosol droplets of well-defined size and composition at high (90%) and low (40%) relative humidity (RH) upwards of 40 min. When compared with the ancestral virus, the infectivity of the Delta variant displayed different decay profiles. At low RH, a loss of viral infectivity of approximately 55% was observed over the initial 5 s for both variants. Regardless of RH and variant, greater than 95% of the viral infectivity was lost after 40 min of being aerosolized. Aero-stability of the variants correlate with their sensitivities to alkaline pH. Removal of all acidic vapours dramatically increased the rate of infectivity decay, with 90% loss after 2 min, while the addition of nitric acid vapour improved aero-stability. Similar aero-stability in droplets of artificial saliva and growth medium was observed. A model to predict loss of viral infectivity is proposed: at high RH, the high pH of exhaled aerosol drives viral infectivity loss; at low RH, high salt content limits the loss of viral infectivity.

Original language	English
Article number	20230062
Journal	Journal of the Royal Society Interface
Volume	20
Issue number	203
DOIs	https://doi.org/10.1098/rsif.2023.0062
Publication status	Published - 21 Jun 2023

Bibliographical note

Funding Information:
This work was funded by the National Institute for Health Research-UK Research and Innovation (UKRI) rapid COVID-19 call, the Elizabeth Blackwell Institute for Health Research, the University of Bristol and the Medical Research Council. Additionally, this work was supported by funding from the PROTECT COVID-19 National Core Study on transmission and environment, managed by the Health and Safety Executive on behalf of Her Majesty's Government. A.H. and M.O.-F. received funding from the Biotechnology and Biological Sciences Research Council, Projects BB/T011688/1 and BB/W00884X/1. A.D.D. is a member of the G2P-UK National Virology consortium funded by the Medical Research Council/UKRI (grant no. MR/W005611/1) that supplied SARS-CoV-2 variants. H.O. is supported by funding from the Defence Science and Technology Laboratory and the Engineering and Physical Sciences Research Council. Acknowledgements

Publisher Copyright:
© 2023 The Authors.

Research Groups and Themes

Physical & Theoretical

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This is the final published version of the article (version of record). It first appeared online via Royal Society Publishing at https://doi.org/10.1098/rsif.2023.0062. Please refer to any applicable terms of use of the publisher
Final published version, 1.1 MBLicence: CC BY

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1 Finished
1 Active

EPSRC Centre for Doctoral Training in Aerosol Science
Reid, J. P. (Principal Investigator)
1/04/19 → 30/09/27
Project: Research
Exploring the Factors that Determine the Survival of Viruses in Aerosols and Droplets
Reid, J. P. (Principal Investigator)
1/04/22 → 31/03/25
Project: Research

The investigation of the dynamics of exhaled respiratory aerosols
Tian, J.-H. (Author), Reid, J. (Supervisor), 1 Oct 2024
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)

File
‘Coughs and sneezes spread diseases’. The replication and modelling of infectious respiratory aerosol.
Alexander, R. W. (Author), Hill, D. J. (Supervisor) & Reid, J. P. (Supervisor), 18 Mar 2025
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)

File

Cite this

Haddrell, A. E., Otero-Fernandez, M., Oswin, H., Cogan, T. A., Bazire, J., Tian, J., Alexander, R. W., Mann, J. F. S., Hill, D. J., Finn, A. H. R., Davidson, A. D., & Reid, J. P. (2023). Differences in airborne stability of SARS-CoV-2 variants of concern is impacted by alkalinity of surrogates of respiratory aerosol. Journal of the Royal Society Interface, 20(203), Article 20230062. https://doi.org/10.1098/rsif.2023.0062

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title = "Differences in airborne stability of SARS-CoV-2 variants of concern is impacted by alkalinity of surrogates of respiratory aerosol",

abstract = "The mechanistic factors hypothesized to be key drivers for the loss of infectivity of viruses in the aerosol phase often remain speculative. Using a next-generation bioaerosol technology, we report measurements of the aero-stability of several SARS-CoV-2 variants of concern in aerosol droplets of well-defined size and composition at high (90\%) and low (40\%) relative humidity (RH) upwards of 40 min. When compared with the ancestral virus, the infectivity of the Delta variant displayed different decay profiles. At low RH, a loss of viral infectivity of approximately 55\% was observed over the initial 5 s for both variants. Regardless of RH and variant, greater than 95\% of the viral infectivity was lost after 40 min of being aerosolized. Aero-stability of the variants correlate with their sensitivities to alkaline pH. Removal of all acidic vapours dramatically increased the rate of infectivity decay, with 90\% loss after 2 min, while the addition of nitric acid vapour improved aero-stability. Similar aero-stability in droplets of artificial saliva and growth medium was observed. A model to predict loss of viral infectivity is proposed: at high RH, the high pH of exhaled aerosol drives viral infectivity loss; at low RH, high salt content limits the loss of viral infectivity.",

author = "Haddrell, \{Allen E\} and Mara Otero-Fernandez and Henry Oswin and Cogan, \{Tristan A\} and James Bazire and Jiang-han Tian and Alexander, \{Robert W\} and Mann, \{Jamie F S\} and Hill, \{Darryl J\} and Finn, \{Adam H R\} and Davidson, \{Andrew D\} and Reid, \{Jonathan P\}",

note = "Funding Information: This work was funded by the National Institute for Health Research-UK Research and Innovation (UKRI) rapid COVID-19 call, the Elizabeth Blackwell Institute for Health Research, the University of Bristol and the Medical Research Council. Additionally, this work was supported by funding from the PROTECT COVID-19 National Core Study on transmission and environment, managed by the Health and Safety Executive on behalf of Her Majesty's Government. A.H. and M.O.-F. received funding from the Biotechnology and Biological Sciences Research Council, Projects BB/T011688/1 and BB/W00884X/1. A.D.D. is a member of the G2P-UK National Virology consortium funded by the Medical Research Council/UKRI (grant no. MR/W005611/1) that supplied SARS-CoV-2 variants. H.O. is supported by funding from the Defence Science and Technology Laboratory and the Engineering and Physical Sciences Research Council. Acknowledgements Publisher Copyright: {\textcopyright} 2023 The Authors.",

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Haddrell, AE, Otero-Fernandez, M, Oswin, H, Cogan, TA, Bazire, J, Tian, J, Alexander, RW , Mann, JFS , Hill, DJ , Finn, AHR , Davidson, AD & Reid, JP 2023, 'Differences in airborne stability of SARS-CoV-2 variants of concern is impacted by alkalinity of surrogates of respiratory aerosol', Journal of the Royal Society Interface, vol. 20, no. 203, 20230062. https://doi.org/10.1098/rsif.2023.0062

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AU - Haddrell, Allen E

AU - Otero-Fernandez, Mara

AU - Oswin, Henry

AU - Cogan, Tristan A

AU - Bazire, James

AU - Tian, Jiang-han

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AU - Mann, Jamie F S

AU - Hill, Darryl J

AU - Finn, Adam H R

AU - Davidson, Andrew D

AU - Reid, Jonathan P

N1 - Funding Information: This work was funded by the National Institute for Health Research-UK Research and Innovation (UKRI) rapid COVID-19 call, the Elizabeth Blackwell Institute for Health Research, the University of Bristol and the Medical Research Council. Additionally, this work was supported by funding from the PROTECT COVID-19 National Core Study on transmission and environment, managed by the Health and Safety Executive on behalf of Her Majesty's Government. A.H. and M.O.-F. received funding from the Biotechnology and Biological Sciences Research Council, Projects BB/T011688/1 and BB/W00884X/1. A.D.D. is a member of the G2P-UK National Virology consortium funded by the Medical Research Council/UKRI (grant no. MR/W005611/1) that supplied SARS-CoV-2 variants. H.O. is supported by funding from the Defence Science and Technology Laboratory and the Engineering and Physical Sciences Research Council. Acknowledgements Publisher Copyright: © 2023 The Authors.

PY - 2023/6/21

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N2 - The mechanistic factors hypothesized to be key drivers for the loss of infectivity of viruses in the aerosol phase often remain speculative. Using a next-generation bioaerosol technology, we report measurements of the aero-stability of several SARS-CoV-2 variants of concern in aerosol droplets of well-defined size and composition at high (90%) and low (40%) relative humidity (RH) upwards of 40 min. When compared with the ancestral virus, the infectivity of the Delta variant displayed different decay profiles. At low RH, a loss of viral infectivity of approximately 55% was observed over the initial 5 s for both variants. Regardless of RH and variant, greater than 95% of the viral infectivity was lost after 40 min of being aerosolized. Aero-stability of the variants correlate with their sensitivities to alkaline pH. Removal of all acidic vapours dramatically increased the rate of infectivity decay, with 90% loss after 2 min, while the addition of nitric acid vapour improved aero-stability. Similar aero-stability in droplets of artificial saliva and growth medium was observed. A model to predict loss of viral infectivity is proposed: at high RH, the high pH of exhaled aerosol drives viral infectivity loss; at low RH, high salt content limits the loss of viral infectivity.

AB - The mechanistic factors hypothesized to be key drivers for the loss of infectivity of viruses in the aerosol phase often remain speculative. Using a next-generation bioaerosol technology, we report measurements of the aero-stability of several SARS-CoV-2 variants of concern in aerosol droplets of well-defined size and composition at high (90%) and low (40%) relative humidity (RH) upwards of 40 min. When compared with the ancestral virus, the infectivity of the Delta variant displayed different decay profiles. At low RH, a loss of viral infectivity of approximately 55% was observed over the initial 5 s for both variants. Regardless of RH and variant, greater than 95% of the viral infectivity was lost after 40 min of being aerosolized. Aero-stability of the variants correlate with their sensitivities to alkaline pH. Removal of all acidic vapours dramatically increased the rate of infectivity decay, with 90% loss after 2 min, while the addition of nitric acid vapour improved aero-stability. Similar aero-stability in droplets of artificial saliva and growth medium was observed. A model to predict loss of viral infectivity is proposed: at high RH, the high pH of exhaled aerosol drives viral infectivity loss; at low RH, high salt content limits the loss of viral infectivity.

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DO - 10.1098/rsif.2023.0062

M3 - Article (Academic Journal)

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SN - 1742-5689

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JO - Journal of the Royal Society Interface

JF - Journal of the Royal Society Interface

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M1 - 20230062

ER -

Differences in airborne stability of SARS-CoV-2 variants of concern is impacted by alkalinity of surrogates of respiratory aerosol

Abstract

Bibliographical note

Research Groups and Themes

Access to Document

Handle.net

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Projects

EPSRC Centre for Doctoral Training in Aerosol Science

Exploring the Factors that Determine the Survival of Viruses in Aerosols and Droplets

Student theses

The investigation of the dynamics of exhaled respiratory aerosols

‘Coughs and sneezes spread diseases’. The replication and modelling of infectious respiratory aerosol.

Cite this