Reply to Klein et al.: The importance of aerosol pH for airborne respiratory virus transmission

Oswin, Henry; Haddrell, Allen E.; Otero-Fernandez, Mara; Mann, J. Adin; Cogan, Tristan A; Hilditch, Thomas G; Tian, Jianghan; Hardy, Dan; Hill, David J.; Finn, Adam; Davidson, Andrew D.; Reid, Jonathan P.

doi:10.1073/pnas.2212556119

Cited by 4 publications

(1 citation statement)

References 9 publications

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“…Experiments in which virus-containing aerosol particles were exposed to controlled levels of relative or absolute humidity were initiated as early as the 1940s (e.g., Loosli et al, 1943 andEdward et al, 1943 with animal models) although there is still no consensus concerning the effect of this environmental factor on virus infectivity. Conversely, the impact of vapor partitioning of CO 2 and of acidic gases in the ambient air on particle pH and subsequent virus inactivation has only recently become a topic of scientific interest and is still widely debated Oswin et al, 2022a;Luo et al, 2022;Klein et al, 2022;Oswin et al, 2022b). Experiments that investigated the dependence of airborne virus infectivity on relative or absolute humidity have been reviewed by Sobsey and Meschke (2003), , and Božič and Kanduč (2021).…”

Section: Introductionmentioning

confidence: 99%

Dependence of aerosol-borne influenza A virus infectivity on relative humidity and aerosol composition

Motos,

Schaub,

David

et al. 2024

Preprint

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We describe a novel biosafety aerosol chamber equipped with state-of-the-art instrumentation for bubble-bursting aerosol generation, size distribution measurement, and condensation-growth collection to minimize sampling artifacts when measuring virus infectivity in aerosol particles. Using this facility, we investigated the effect of relative humidity (RH) in very clean air without trace gases (except ~400 ppm CO2) on the preservation of influenza A virus (IAV) infectivity in saline aerosol particles. We characterized infectivity in terms of 99%-inactivation time, t99, a metric we consider most relevant to airborne virus transmission. The viruses remained infectious for a long time, namely t99 > 5 h, if RH < 30% and the particles effloresced. Under intermediate conditions of humidity (40% < RH < 70%), the loss of infectivity was the most rapid (t99 ≈ 15-20 min, and up to t99 ≈ 35 min at 95% RH). This is more than an order of magnitude faster than suggested by many previous studies of aerosol-borne IAV, possibly due to the use of matrices containing organic molecules, such as proteins, with protective effects for the virus. We tested this hypothesis by adding sucrose to our aerosolization medium and, indeed, observed protection of IAV at intermediate RH (55 %). Interestingly, the t99 of our measurements are also systematically lower than those in 1-μL droplet measurements of organic-free saline solutions, which cannot be explained by particle size effects alone.

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Section: Introductionmentioning

confidence: 99%

Dependence of aerosol-borne influenza A virus infectivity on relative humidity and aerosol composition

Motos,

Schaub,

David

et al. 2024

Preprint

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Indoor air humidity revisited: Impact on acute symptoms, work productivity, and risk of influenza and COVID-19 infection

Wolkoff

2024

International Journal of Hygiene and Environmental Health

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Ambient carbon dioxide concentration correlates with SARS-CoV-2 aerostability and infection risk

Haddrell,

Oswin,

Otero-Fernandez

et al. 2024

Nat Commun

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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.

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Reply to Klein et al.: The importance of aerosol pH for airborne respiratory virus transmission

Cited by 4 publications

References 9 publications

Dependence of aerosol-borne influenza A virus infectivity on relative humidity and aerosol composition

Dependence of aerosol-borne influenza A virus infectivity on relative humidity and aerosol composition

Indoor air humidity revisited: Impact on acute symptoms, work productivity, and risk of influenza and COVID-19 infection

Ambient carbon dioxide concentration correlates with SARS-CoV-2 aerostability and infection risk

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