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

引起疾病的微生物，如细菌和病毒，可通过直接(人与人之间)、间接(与受污染表面接触)和空气传播途径传播。可呼吸的小颗粒(直径10微米)和较大的水滴(高达100微米，大约是人类头发直径的两倍)可以在空气中停留几分钟到几个小时，并通过咳嗽、打喷嚏、说话和呼吸排放。较大的液滴在短距离内非常迅速地沉降，污染表面(称为富马物)。虽然一些疾病的传播，如结核病和麻疹，表现出优先通过空气传播，但其他疾病，如流感和诺沃克病毒，是机会性的。必须优先确定这些不同传播方式占主导地位的情况，并澄清缓解这些传播方式的方法。这些知识有助于实施非药物干预措施，如物理距离和使用适当的个人防护装备，如口罩。此外，在临床背景下，可以看到许多气雾剂产生程序的广泛使用，这些程序知之甚少，但可能会在空气中携带病原体，例如在牙科手术和麻醉中。尽管人们认识到气雾剂和水滴在微生物传播中的重要性，但决定减少微生物传播的证据基础往往仍然是流行病学的。强有力的创新工具用于研究控制气雾剂、液滴和混合物中病原体生存的因素，对于推动我们的理解至关重要。利用布里斯托尔大学开发的新技术平台，我们将提供一个全面的框架，用于了解控制SARS-CoV-2病毒生存的因素，即气雾剂、微滴和混合物中新冠肺炎的原因。我们已经开发了一个定制的系统来研究微生物在气雾剂和含有被称为名人的微生物的液滴中的生存情况。我们将在最近投入使用的最先进的设施中研究SARS-CoV-2病毒(在呼吸道飞沫中)与其直接环境之间的相互作用。通过将大小相同的气雾滴与已知病毒载量悬浮一段特定时间，将测量病毒的存活率，并研究灭活措施的影响。更具体地说，我们将全面探索SARS-CoV-2病毒在不同环境条件(相对湿度和温度)下不同大小的液滴中的生存情况，以及在表面沉积的真实模拟混合物中的生存情况。我们还将探讨光照和大气氧化剂(露天系数)以及颗粒大小和水分含量的动态变化率对液滴/气溶胶生成的影响(即干燥/干燥动力学对呼出的影响)。将检查SARS-CoV-2病毒的不同变种的存活率。这个项目将建立在初步工作的基础上，这些工作已经证实和验证了我们的实验方法。这项更全面的工作将为非药物干预提供信息，如社会距离、建议的室内操作温度和湿度(例如医院、疗养院、运输)和其他灭活方法(例如光和氧化剂)。除了这些直接的研究，这项技术将是灵活的，为研究更广泛的重要空气传播病原体打开了机会。

The transmission of microbes which cause disease between humans, such as bacteria and viruses, can occur by direct (person-to-person), indirect (contact with contaminated surfaces) and airborne routes. Small aerosol particles of a respirable size (<10 micrometres diameter) and larger droplets (up to 100 micrometres, about twice the diameter of a human hair) can remain airborne for minutes to hours and are emitted by coughing, sneezing, speaking and breathing. Larger droplets settle very quickly over short distances contaminating surfaces (referred to as fomites). Although the transmission of some diseases, such as tuberculosis and measles, show preferential airborne transmission, other diseases, such as influenza and norovirus, are opportunistic. Identifying both the circumstances when these different modes of transmission are dominant and clarifying ways to mitigate them must be priorities. Such knowledge informs the implementation of non-pharmaceutical interventions, such as physical distancing and the use of appropriate personal protective equipment such as face masks. Further, the clinical context sees the wide use of many aerosol generating procedures that are poorly understood but could carry pathogens through the air, for example in dental procedures and in anaesthesia. Despite the recognised importance of aerosols and droplets in the transmission of microbes, the evidence-base on which decisions are made to mitigate microbe transmission often remain epidemiological. Robust innovative instruments for studying the factors that control the survival of pathogens in aerosols, droplets and fomites are crucial to move our understanding forward. Using a novel technology platform developed at the University of Bristol, we will deliver a comprehensive framework for understanding the factors that control the survival of the virus SARS-CoV-2, the cause of COVID-19 in aerosols, droplets and fomites. We have developed a bespoke system to study how well microbes survive in aerosols and droplets containing microbes referred to as CELEBS. We will study the interactions between the SARS-CoV-2 virus (in respiratory droplets) and its immediate environment in a recently commissioned state of the art facility. By levitating a known number of aerosol droplets of identical size with a known viral load for a specified period of time, the survival of the virus will be measured and the impact of inactivation measures studied. More specifically, we will fully explore the survival of the SARS-CoV-2 virus in droplets of varying size exposed to varying environmental conditions (relative humidity and temperature) and in realistic simulated fomites deposited on surfaces. We will also explore the influence of light and atmospheric oxidants (open air factor) and the rate of dynamic changes in particle size and moisture content upon droplet/aerosol generation (i.e. desiccation/drying kinetics on exhalation). The survival of different variants of the SARS-CoV-2 virus will be examined. This project will build on preliminary work that has confirmed and validated our experimental approach. This more comprehensive work will provide clarity to inform non-pharmaceutical interventions such as social distancing, recommended indoor operating temperatures and humidities (e.g. hospitals, care homes, transport) and other methods of inactivation (e.g. light and oxidants). Extending beyond these immediate studies, the technique will be flexible, opening up opportunities to study a wider range of important airborne pathogens.