French Andrea J, Longest Alexandra K, Pan Jin, Vikesland Peter J, Duggal Nisha K, Lakdawala Seema S, Marr Linsey C
Department of Microbiology & Molecular Genetics, University of Pittsburgh School of Medicine, Pittsburgh, PA.
Department of Civil and Environmental Engineering, Virginia Tech, Blacksburg, VA.
bioRxiv. 2022 Jul 27:2022.07.26.501658. doi: 10.1101/2022.07.26.501658.
Efficient spread of respiratory viruses requires the virus to maintain infectivity in the environment. Environmental stability of viruses can be influenced by many factors, including temperature and humidity. Our study measured the impact of initial droplet volume (50, 5, and 1 µL) and relative humidity (RH: 40%, 65%, and 85%) on the stability of influenza A virus, bacteriophage, Phi6, a common surrogate for enveloped viruses, and SARS-CoV-2 under a limited set of conditions. Our data suggest that the drying time required for the droplets to reach quasi-equilibrium (i.e. a plateau in mass) varied with RH and initial droplet volume. The macroscale physical characteristics of the droplets at quasi-equilibrium varied with RH but not with initial droplet volume. We observed more rapid virus decay when the droplets were still wet and undergoing evaporation, and slower decay after the droplets had dried. Initial droplet volume had a major effect on virus viability over the first few hours; whereby the decay rate of influenza virus was faster in smaller droplets. In general, influenza virus and SARS-CoV-2 decayed similarly. Overall, this study suggests that virus decay in media is closely correlated with the extent of droplet evaporation, which is controlled by RH. Taken together, these data suggest that decay of different viruses is more similar at higher RH and in smaller droplets and is distinct at lower RH and in larger droplets. Importantly, accurate assessment of transmission risk requires use of physiologically relevant droplet volumes and careful consideration of the use of surrogates.
National Institute of Allergy and Infectious Diseases, National Institute of Neurological Disorders and Stroke, National Institutes of Health; Department of Health and Human Services; Flu Lab.
During the COVID-19 pandemic, policy decisions were being driven by virus stability experiments involving SARS-CoV-2 applied to surfaces in large droplets at various humidity conditions. The results of our study indicate that determination of half-lives for emerging pathogens in large droplets likely over-estimates transmission risk for contaminated surfaces, as occurred during the COVID-19 pandemic. Our study implicates the need for the use of physiologically relevant droplet sizes with use of relevant surrogates in addition to what is already known about the importance of physiologically relevant media for risk assessment of future emerging pathogens.
呼吸道病毒的有效传播要求病毒在环境中保持感染力。病毒的环境稳定性会受到许多因素影响，包括温度和湿度。我们的研究在一组有限条件下，测量了初始液滴体积（50、5和1微升）和相对湿度（RH：40%、65%和85%）对甲型流感病毒、噬菌体Phi6（一种常见的包膜病毒替代物）以及严重急性呼吸综合征冠状病毒2（SARS-CoV-2）稳定性的影响。我们的数据表明，液滴达到准平衡（即质量达到平稳状态）所需的干燥时间随相对湿度和初始液滴体积而变化。准平衡时液滴的宏观物理特性随相对湿度而变化，但不随初始液滴体积而变化。我们观察到，当液滴仍处于湿润且正在蒸发状态时，病毒衰减更快，而在液滴干燥后衰减较慢。在最初几个小时内，初始液滴体积对病毒活力有重大影响；较小液滴中流感病毒的衰减速率更快。总体而言，流感病毒和SARS-CoV-2的衰减情况相似。这项研究总体表明，介质中的病毒衰减与液滴蒸发程度密切相关，而液滴蒸发程度由相对湿度控制。综合来看，这些数据表明，在较高相对湿度和较小液滴中，不同病毒的衰减更为相似，而在较低相对湿度和较大液滴中则有所不同。重要的是，准确评估传播风险需要使用生理相关的液滴体积，并仔细考虑替代物的使用。
美国国立过敏与传染病研究所、美国国立神经疾病与中风研究所、美国国立卫生研究院；美国卫生与公众服务部；流感实验室。
在2019冠状病毒病大流行期间，政策决策是由涉及在各种湿度条件下将SARS-CoV-2应用于大液滴表面的病毒稳定性实验推动的。我们的研究结果表明，确定大液滴中新兴病原体的半衰期可能高估了受污染表面的传播风险，就像2019冠状病毒病大流行期间那样。我们的研究表明，除了已知生理相关介质对未来新兴病原体风险评估的重要性外，还需要使用生理相关的液滴大小并使用相关替代物。
