Airborne transmission of respiratory viruses.
Airborne transmission of respiratory viruses.
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DOI：
10.1126/science.abd9149
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发表时间：
2021-08-27
期刊：
影响因子：
--
通讯作者：
Marr LC
中科院分区：
文献类型：
--
作者：
Wang CC;Prather KA;Sznitman J;Jimenez JL;Lakdawala SS;Tufekci Z;Marr LC
COVID-19 大流行凸显了关于呼吸道病原体如何在宿主之间传播的争议和未知数。传统上，人们认为呼吸道病原体通过咳嗽时产生的大飞沫以及通过接触受污染的表面（污染物）在人与人之间传播。然而，已知几种呼吸道病原体通过细小的呼吸道气溶胶传播，这些气溶胶可以漂浮并在气流中传播，从而感染距离感染者近距离和远距离吸入这些病原体的人。王等人。回顾通过研究严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 感染和其他呼吸道病原体的传播而获得的了解空气传播的最新进展。作者认为，空气传播可能是包括 SARS-CoV-2 在内的几种呼吸道病原体的主要传播形式，进一步了解空气传播途径感染的机制将为缓解措施提供更好的信息。 —GKA A Review 讨论了包括冠状病毒在内的呼吸道病毒通过空气传播的科学依据和控制因素。接触感染者咳嗽和打喷嚏时产生的飞沫或接触被飞沫污染的表面（污染物）已被广泛认为是呼吸道病原体的主要传播方式。空气传播传统上被定义为涉及吸入小于 5 μm 的传染性气溶胶或“飞沫核”，且主要发生在距离感染者 >1 至 2 m 的地方，并且这种传播被认为仅与“异常”疾病有关。然而，有强有力的证据支持许多呼吸道病毒通过空气传播，包括严重急性呼吸综合征冠状病毒（SARS-CoV）、中东呼吸综合征（MERS）冠状病毒、流感病毒、人鼻病毒和呼吸道合胞病毒（RSV）。 COVID-19 大流行期间，凸显了飞沫、污染物和空气传播的传统观点的局限性。仅靠 SARS-CoV-2 的飞沫和污染物传播无法解释 COVID-19 大流行期间观察到的众多超级传播事件以及室内和室外环境之间传播的差异。围绕 COVID-19 如何传播以及需要采取哪些干预措施来控制这一流行病的争议表明，迫切需要更好地了解呼吸道病毒的空气传播途径，这将有助于制定更明智的策略来减轻呼吸道感染的传播。各种呼气活动均可产生呼吸道飞沫和气溶胶。气溶胶测量技术（例如空气动力学和扫描迁移率粒径测量）的进步表明，大多数呼出的气溶胶小于 5 μm，对于大多数呼吸活动（包括呼吸、说话和咳嗽时产生的气溶胶），很大一部分小于 1 μm。呼出的气溶胶以多种尺寸模式出现，这些模式与呼吸道中不同的产生部位和产生机制相关。尽管历史上使用 5 μm 来区分气溶胶和液滴，但气溶胶和液滴之间的尺寸区别应为 100 μm，这代表从 1.5 m 高度在静止空气中保持悬浮超过 5 s、通常到达距发射器 1 至 2 m 距离（取决于携带气溶胶的气流速度）并可被吸入的最大颗粒尺寸。感染者产生的气溶胶可能含有传染性病毒，研究表明病毒在微小气溶胶（<5μm）中富集。载有病毒的气溶胶的输送受到气溶胶本身的理化性质和环境因素的影响，包括温度、相对湿度、紫外线、气流和通风。一旦吸入，含有病毒的气溶胶就会沉积在呼吸道的不同部位。较大的气溶胶往往沉积在上呼吸道；然而，较小的气溶胶虽然也可以沉积在那里，但可以深入肺部的肺泡区域。通风对传播的强烈影响、室内和室外传播之间的明显差异、有据可查的远距离传播、尽管使用口罩和护目镜仍观察到的 SARS-CoV-2 传播、SARS-CoV-2 室内超级传播事件的高频率、动物实验和气流模拟，为空气传播提供了强有力且明确的证据。人们发现 SARS-CoV-2 的雾沫传播效率要低得多，并且只有当人与人交谈时彼此距离在 0.2 m 以内时，飞沫才占主导地位。尽管感染者在呼气活动期间可以产生气溶胶和飞沫，但飞沫在几秒钟内迅速落到地面或表面，从而在飞沫上留下富集的气溶胶。空气传播途径可能有助于其他呼吸道病毒的传播，这些病毒的传播以前被认为是由飞沫驱动的。世界卫生组织 (WHO) 和美国疾病控制与预防中心 (CDC) 已正式承认吸入载有病毒的气溶胶是 2021 年短距离和远距离传播 COVID-19 的主要传播方式。病原体的空气传播一直被大大低估，主要是因为对气溶胶在空气中的行为了解不够，至少部分是因为 对轶事观察的错误归因。鉴于缺乏飞沫和污染物传播的证据，以及气溶胶传播多种呼吸道病毒的证据越来越多，我们必须承认，空气传播比以前认识到的更为普遍。鉴于我们对 SARS-CoV-2 感染的了解，需要重新评估所有呼吸道传染病的气溶胶传播途径。必须采取额外的预防措施，以减轻短距离和长距离的气溶胶传播，特别注意通风、气流、空气过滤、紫外线消毒和口罩佩戴。这些干预措施是结束当前大流行和预防未来疫情爆发的重要工具。载有病毒的气溶胶（<100 I1/4m）首先由感染者通过呼气活动产生，通过呼气活动被呼出并输送到环境中。如果它们仍然具有传染性，它们可能会被潜在宿主吸入以引发新的感染。与飞沫 (>100 I1/4m) 相比，气溶胶可以在空气中停留数小时，并从感染者呼出的气溶胶传播到 1 至 2 m 之外，从而在短距离和长距离内引起新的感染。 COVID-19 大流行暴露了我们对呼吸道病毒传播途径的理解存在严重的知识差距，需要更新这一传统观点。飞沫和空气传播的长期定义并没有解释携带病毒的呼吸道飞沫和气溶胶通过空气传播并导致感染的机制。在这篇综述中，我们讨论了有关呼吸道病毒通过气溶胶传播的现有证据——它们是如何产生、传播和沉积的，以及影响飞沫喷雾沉积与气溶胶吸入作为传播方式的相对贡献的因素。通过对严重急性呼吸综合征冠状病毒 2 (SARS-CoV-2) 感染的研究，加深了对气溶胶传播的了解，需要重新评估其他呼吸道病毒的主要传播途径，这将有助于采取更明智的控制措施，减少空气传播。
The COVID-19 pandemic has highlighted controversies and unknowns about how respiratory pathogens spread between hosts. Traditionally, it was thought that respiratory pathogens spread between people through large droplets produced in coughs and through contact with contaminated surfaces (fomites). However, several respiratory pathogens are known to spread through small respiratory aerosols, which can float and travel in air flows, infecting people who inhale them at short and long distances from the infected person. Wang et al. review recent advances in understanding airborne transmission gained from studying the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and other respiratory pathogens. The authors suggest that airborne transmission may be the dominant form of transmission for several respiratory pathogens, including SARS-CoV-2, and that further understanding of the mechanisms underlying infection from the airborne route will better inform mitigation measures. —GKA A Review discusses the scientific basis of and factors controlling airborne transmission of respiratory viruses including coronavirus. Exposure to droplets produced in the coughs and sneezes of infected individuals or contact with droplet-contaminated surfaces (fomites) have been widely perceived as the dominant transmission modes for respiratory pathogens. Airborne transmission is traditionally defined as involving the inhalation of infectious aerosols or “droplet nuclei” smaller than 5 μm and mainly at a distance of >1 to 2 m away from the infected individual, and such transmission has been thought to be relevant only for “unusual” diseases. However, there is robust evidence supporting the airborne transmission of many respiratory viruses, including severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome (MERS)–CoV, influenza virus, human rhinovirus, and respiratory syncytial virus (RSV). The limitations of traditional views of droplet, fomite, and airborne transmission were illuminated during the COVID-19 pandemic. Droplet and fomite transmission of SARS-CoV-2 alone cannot account for the numerous superspreading events and differences in transmission between indoor and outdoor environments observed during the COVID-19 pandemic. Controversy surrounding how COVID-19 is transmitted and what interventions are needed to control the pandemic has revealed a critical need to better understand the airborne transmission pathway of respiratory viruses, which will allow for better-informed strategies to mitigate the transmission of respiratory infections. Respiratory droplets and aerosols can be generated by various expiratory activities. Advances in aerosol measurement techniques, such as aerodynamic and scanning mobility particle sizing, have shown that the majority of exhaled aerosols are smaller than 5 μm, and a large fraction are <1 μm for most respiratory activities, including those produced during breathing, talking, and coughing. Exhaled aerosols occur in multiple size modes that are associated with different generation sites and production mechanisms in the respiratory tract. Although 5 μm has been used historically to distinguish aerosols from droplets, the size distinction between aerosols and droplets should be 100 μm, which represents the largest particle size that can remain suspended in still air for more than 5 s from a height of 1.5 m, typically reach a distance of 1 to 2 m from the emitter (depending on the velocity of airflow carrying the aerosols), and can be inhaled. Aerosols produced by an infected individual may contain infectious viruses, and studies have shown that viruses are enriched in small aerosols (<5 μm). The transport of virus-laden aerosols is affected by the physicochemical properties of aerosols themselves and environmental factors, including temperature, relative humidity, ultraviolet radiation, airflow, and ventilation. Once inhaled, virus-laden aerosols can deposit in different parts of the respiratory tract. Larger aerosols tend to be deposited in the upper airway; however, smaller aerosols, although they can also be deposited there, can penetrate deep into the alveolar region of the lungs. The strong effect of ventilation on transmission, the distinct difference between indoor and outdoor transmission, well-documented long-range transmission, the observed transmission of SARS-CoV-2 despite the use of masks and eye protection, the high frequency of indoor superspreading events of SARS-CoV-2, animal experiments, and airflow simulations provide strong and unequivocal evidence for airborne transmission. Fomite transmission of SARS-CoV-2 has been found to be far less efficient, and droplets are only dominant when individuals are within 0.2 m of each other when talking. Although both aerosols and droplets can be produced by infected individuals during expiratory activities, droplets fall quickly to the ground or surfaces within seconds, leaving an enrichment of aerosols over droplets. The airborne pathway likely contributes to the spread of other respiratory viruses whose transmission was previously characterized as droplet driven. The World Health Organization (WHO) and the US Centers for Disease Control and Prevention (CDC) have officially acknowledged the inhalation of virus-laden aerosols as a main transmission mode in spreading COVID-19 at both short and long ranges in 2021. Airborne transmission of pathogens has been vastly underappreciated, mostly because of an insufficient understanding about the airborne behavior of aerosols and at least partially because of the misattribution of anecdotal observations. Given the lack of evidence for droplet and fomite transmission and the increasingly strong evidence for aerosols in transmitting numerous respiratory viruses, we must acknowledge that airborne transmission is much more prevalent than previously recognized. Given all that we have learned about SARS-CoV-2 infection, the aerosol transmission pathway needs to be reevaluated for all respiratory infectious diseases. Additional precautionary measures must be implemented for mitigating aerosol transmission at both short and long ranges, with particular attention to ventilation, airflows, air filtration, UV disinfection, and mask fit. These interventions are critical tools for ending the current pandemic and preventing future outbreaks. Virus-laden aerosols (<100 I1/4m) are first generated by an infected individual through expiratory activities, through which they are exhaled and transported in the environment. They may be inhaled by a potential host to initiate a new infection, provided that they remain infectious. In contrast to droplets (>100 I1/4m), aerosols can linger in air for hours and travel beyond 1 to 2 m from the infected individual who exhales them, causing new infections at both short and long ranges. The COVID-19 pandemic has revealed critical knowledge gaps in our understanding of and a need to update the traditional view of transmission pathways for respiratory viruses. The long-standing definitions of droplet and airborne transmission do not account for the mechanisms by which virus-laden respiratory droplets and aerosols travel through the air and lead to infection. In this Review, we discuss current evidence regarding the transmission of respiratory viruses by aerosols—how they are generated, transported, and deposited, as well as the factors affecting the relative contributions of droplet-spray deposition versus aerosol inhalation as modes of transmission. Improved understanding of aerosol transmission brought about by studies of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection requires a reevaluation of the major transmission pathways for other respiratory viruses, which will allow better-informed controls to reduce airborne transmission.
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DOI：
10.1073/pnas.2015482118
发表时间：
2021-02-23
影响因子：
11.1
作者：
Azimi P;Keshavarz Z;Cedeno Laurent JG;Stephens B;Allen JG
通讯作者：
Allen JG
影响因子：
82.9
作者：
Adam, Dillon C.;Wu, Peng;Cowling, Benjamin J.
通讯作者：
Cowling, Benjamin J.
影响因子：
6.4
作者：
Bischoff, Werner E.;McNall, Rebecca J.;Stehle, John R., Jr.
通讯作者：
Stehle, John R., Jr.
影响因子：
3.7
作者：
Bourouiba, Lydia;Dehandschoewercker, Eline;Bush, John W. M.
通讯作者：
Bush, John W. M.
影响因子：
6.4
作者：
Booth, TF;Kournikakis, B;Plummer, F
通讯作者：
Plummer, F