239名科学家称新冠病毒空气传播风险或被低估，世卫组织回应
The following article is from 消毒学进展 Author 消毒学进展
近日，据《纽约时报》报道，239名来自32个国家不同的科学和工程领域，包括病毒学、气溶胶物理学、流动力学、暴露和流行病学、医学和建筑工程专家发表联名公开信，确信新冠病毒可以通过空气传播来感染人类，即便是较小的液滴或是颗粒也存在感染性，并且呼吁世卫组织修改应对建议。
此前，世卫组织认为，新冠病毒主要通过呼吸道飞沫在人与人之间传播。只有在某些特定情况下，如给患者进行气管插管时，可能会产生气溶胶，进而出现空气传播。
然而，这些科学家认为，有（比飞沫）更小的颗粒存在，这些更小的颗粒能够在空气中停留更长时间，通过空气传播到更远的距离，被人体吸入后造成感染。他们声称，有新证据表明，空气传播可能比飞沫传播更值得关注。
现在是解决COVID-19
空气传播问题的时候了
It is Time to Address Airborne Transmission of COVID-19
We appeal to the medical community and to the relevant national and international bodies to recognize the potential for airborne spread of COVID-19. There is significant potential for inhalation exposure to viruses in microscopic respiratory droplets (microdroplets) at short to medium distances (up to several meters, or room scale), and we are advocating for the use of preventive measures to mitigate this route of airborne transmission.
我们呼吁医学界、相关国家和国际机构认识到COVID-19通过空气传播的可能性。在短距离至中距离(可达数米或房间内)条件下，暴露于微小呼吸道飞沫（微小液滴）而吸入病毒的可能性很大，我们主张采取相关预防控制措施，以降低空气传播风险。
Studies by the signatories and other scientists have demonstrated beyond any reasonable doubt that viruses are released during exhalation, talking, and coughing in microdroplets small enough to remain aloft in air and pose a risk of exposure at distances beyond 1 to 2 m from an infected individual (see e.g. [1-4]). For example, at typical indoor air velocities [5], a 5 μm droplet will travel tens of meters, much greater than the scale of a typical room, while settling from a height of 1.5 m to the floor. Several retrospective studies conducted after the SARS-CoV-1 epidemic demonstrated that airborne transmission was the most likely mechanism explaining the spatial pattern of infections e.g. [6].Retrospective analysis has shown the same for SARS-CoV-2 [7-10]. In particular, a study in their review of records from a Chinese restaurant, observed no evidence of direct or indirect contact between the three parties [10]. In their review of video records from the restaurant, they observed no evidence of direct or indirect contact between the three parties. Many studies conducted on the spread of other viruses, including respiratory syncytial virus (RSV) [11], Middle East Respiratory Syndrome coronavirus (MERS-CoV) [8], and influenza [2,4], show that viable airborne viruses can be exhaled [2] and/or detected in the indoor environment of infected patients [11-12]. This poses the risk that people sharing such environments can potentially inhale these viruses, resulting in infection and disease. There is every reason to expect that SARS-CoV-2 behaves similarly, and that transmission via airborne microdroplets [10,13] is an important pathway. Viral RNA associated with droplets smaller than 5 μm has been detected in air [14], and the virus has been shown to maintain infectivity in droplets of this size [9]. Other viruses have been shown to survive equally well, if not better, in aerosols compared to droplets on a surface [15].
签名者和其他科学家的研究已经证明，毫无疑问，病毒会在呼气、说话和咳嗽的过程中以微小液滴的形式释放出来，这些微小的液滴足以保持在空中，在超过感染者1到2米以外的距离产生暴露风险。在典型的室内空气流速下，一个5um的液滴会移动数十米，并从1.5米的高度沉降到地面，微小液滴移动的距离比一个典型房间尺寸大得多。SARS-CoV-1流行后进行的几项回顾性研究表明，空气传播机制最有可能解释其空间感染的模式。SARS-CoV-2回顾性分析也表明，该病毒也是如此。特别值得一提的是，在对一家中国餐馆的调查中发现，没有证据表明三方有直接或间接的接触。在查看餐厅的视频记录时，没有发现三方有直接或间接接触的证据。呼吸道合胞病毒(RSV)、中东呼吸综合征冠状病毒(MERS-CoV)、流感等其他病毒的传播研究表明，活病毒可通过呼吸道排出到空气中，并/或在感染者室内环境中检测到，暴露于同一环境的人可能存在吸入这些病毒的风险，从而导致感染和疾病。我们有充分的理由相信SARS-CoV-2具有类似的特点，而通过空气中的微滴传播是一个重要途径。在空气中已检测到与小于5um的微小液滴相关的病毒RNA，并且已证明该病毒在这种大小的液滴中会保持感染性，其他病毒也已经被证明在气溶胶中的存活能力与在表面飞沫中存活能力相当。
The current guidance from numerous international and national bodies focuses on hand washing, maintaining social distancing, and droplet precautions. Most public health organizations, including the World Health Organization (WHO) [16], do not recognize airborne transmission except for aerosol-generating procedures performed in healthcare settings. Hand washing and social distancing are appropriate, but in our view, insufficient to provide protection from virus-carrying respiratory microdroplets released into the air by infected people. This problem is especially acute in indoor or enclosed environments, particularly those that are crowded and have inadequate ventilation [17] relative to the number of occupants and extended exposure periods (as graphically depicted in Figure 1). For example, airborne transmission appears to be the only plausible explanation for several superspreading events investigated which occurred under such conditions e.g. [10], and others where recommended precautions related to direct droplet transmissions were followed.
目前许多国家和国际组织的指南将重点放在洗手、保持社交距离和飞沫传播预防上，大多数公共卫生组织，包括世界卫生组织(WHO)，不认可空气传播，仅认可在医疗机构中实施产生气溶胶操作程序时会发生空气传播。洗手和保持社交距离是正确的，但我们认为，这不足以保护人们不受感染者释放到空气中的携带病毒的呼吸道微小液滴的伤害。这一问题在室内或封闭环境中尤其严重，特别是那些拥挤、通风不良和长时间暴露的环境（如图1）。空气传播似乎是在这种情况下，以及在其他情况下采取了飞沫传播有关的预防措施，而发生的几次超级传播事件的唯一合理解释。
图注：呼吸道微小液滴在(a)通风不足和(b)通风充足的室内环境中的分布
The evidence is admittedly incomplete for all the steps in COVID-19 microdroplet transmission, but it is similarly incomplete for the large droplet and fomite modes of transmission. The airborne transmission mechanism operates in parallel with the large droplet and fomite routes, e.g. [16] that are now the basis of guidance. Following the precautionary principle, we must address every potentially important pathway to slow the spread of COVID-19. The measures that should be taken to mitigate airborne transmission risk include:Provide sufficient and effective ventilation (supply clean outdoor air, minimize recirculating air) particularly in public buildings, workplace environments, schools, hospitals, and aged care homes.Supplement general ventilation with airborne infection controls such as local exhaust, high efficiency air filtration, and germicidal ultraviolet lights.Avoid overcrowding, particularly in public transport and public buildings.
诚然，COVID-19微小液滴传播的证据还不完整，但较大飞沫和污染物传播方式的证据同样不完整。同时考虑空气传播机制与飞沫传播和污染物传播，应是目前指南制订的基础。根据预防的基本原则，我们必须考虑减缓COVID-19传播的每一个可能的重要途径。为降低空气传播风险采取，采取的预防控制措施应包括：在公共场所、工作场所、学校、医院和养老院，提供充分且有效的通风(提供清洁的室外空气，减少室内循环空气)。用局部排气、高效空气过滤和紫外线杀菌灯等空气感染控制措施补充普通的通风。避免过度拥挤，特别是在公共交通工具和公共场所。
Such measures are practical and often can be easily implemented; many are not costly. For example, simple steps such as opening both doors and windows can dramatically increase air flow rates in many buildings. For mechanical systems, organizations such as ASHRAE (the American Society of Heating, Ventilating, and Air-Conditioning Engineers) and REHVA (the Federation of European Heating, Ventilation and Air Conditioning Associations) have already provided guidelines based on the existing evidence of airborne transmission. The measures we propose offer more benefits than potential downsides, even if they can only be partially implemented.
这些措施是切实可行的，往往很容易执行，很多并不昂贵。例如，一些简单的方法，如打开门窗，可以显著增加许多建筑物的空气流量。对于机械通风系统，诸如ASHRAE(美国供暖、通风和空调工程师协会)和REHVA(欧洲供暖、通风和空调协会联合会)等组织已经根据现有的空气传播证据提供了指导方针。我们提出的措施，即使只能部分实施，也会带来更多的好处，而不是潜在的负面影响。
It is understood that there is not as yet universal acceptance of airborne transmission of SARS-CoV2; but in our collective assessment there is more than enough supporting evidence so that the precautionary principle should apply. In order to control the pandemic, pending the availability of a vaccine, all routes of transmission must be interrupted.
据了解，SARS-CoV2的空中传播尚未得到普遍接受，但在我们的集体评估中，已有足够多的证据，支持应当采取空气传播预防控制措施。为了控制大流行，在获得疫苗之前，必须阻断所有传播途径。
We are concerned that the lack of recognition of the risk of airborne transmission of COVID-19 and the lack of clear recommendations on the control measures against the airborne virus will have significant consequences: people may think that they are fully protected by adhering to the current recommendations, but in fact, additional airborne interventions are needed for further reduction of infection risk.
我们担心，对COVID-19空气传播的风险认识不足，和对空气传播防控指南的缺乏，将会产生严重的后果:人们会认为遵照当前的指南，他们已得到完全保护，但事实上，他们需要额外的干预措施以进一步降低感染的风险。
This matter is of heightened significance now, when countries are re-opening following lockdowns - bringing people back to workplaces and students back to schools, colleges, and universities. We hope that our statement will raise awareness that airborne transmission of COVID-19 is a real risk and that control measures, as outlined above, must be added to the other precautions taken, to reduce the severity of the pandemic and save lives.
现在，这一问题具有更大的紧迫性，因为各国在关闭后重新开放，让人们重新回到工作场所，让学生们重新回到学校。我们希望，我们的声明能提高人们的认识，即COVID-19空气传播是一种切实存在的风险，必须在采取其他预防措施的基础上，增加上述空气传播预防控制措施，以减轻大流行的严重程度，挽救更多生命。
Disclaimer: The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of any agency/institution.
免责声明:本文所表达的观点和意见仅为作者个人观点，并不代表任何机构或机构的官方政策或立场。
AcknowledgmentTogether with the authors, 239 scientists support this Commentary, and their affiliations and contact details are listed in the Supplementary.
但目前在实验室
科学家仍然无法从气溶胶当中培养出新冠病毒
对此，世卫组织也进行了回应
世卫组织：
正在评估新冠病毒空气传播风险
当地时间7月7日，世卫组织召开新冠肺炎例行发布会，针对239名科学家联名发表公开信呼吁世卫组织关注新冠病毒空气传播风险，世卫组织感染预防与控制中心技术主管贝妮代塔·阿莱格兰齐表示，过去几个月，世卫组织已与多名该信件署名科学家就相关证据展开讨论与合作，的确有逐渐显露的证据。世卫组织对此类证据持开放态度，并了解其涉及的病毒传播方式以及需要采取的预防措施。
贝妮代塔·阿莱格兰齐指出，尽管该领域研究正在增加，但一些证据并不确定，不能排除在拥挤、封闭等通风条件差的环境中，新冠病毒通过空气传播的可能性，仍需搜集证据并分析。贝妮代塔·阿莱格兰齐同时建议采取尽可能多的防护措施，如避免停留在封闭和拥挤的环境中、做好室内通风工作等。
世卫组织卫生紧急项目技术主管玛丽亚·范·科霍夫表示，世卫组织自4月1日起就与这些科学家保持密切沟通，一直在讨论病毒通过空气和气溶胶进行传播的可能性，世卫组织将发布科学简报总结病毒传播途径。
若理论被证实
或将会产生巨大轰动
但是专家们也指出，防控疫情的具体策略被过分刻板的科学证据所束缚，导致其更新和推广速度非常缓慢。
新南威尔士大学病理学家麦克劳斯（Mary-Louise McLaws）表示，令人恼怒的不是“液滴的大小”，而是这个理论如果被证实后，给社会产生的巨大轰动。
“如果我们开始重新审视气流理论，我们会做好准备去改变先前的一切，”她说，“我认为这是好的，非常好的想法，但是这会对当前受疫情控制的社会产生巨大震动。”
弗吉尼亚理工大学的空气传播病毒学家马尔（Linsey Marr）博士说：“自1946年以来我们就知道咳嗽与谈话都能产生小液滴。”
目前，科学家们尚且没有从呼吸液滴中提取出新冠病毒，但并不代表呼吸液滴不具感染性，马尔博士表示：大多样本来自于通风良好的医院，这会稀释病毒密度。
牛津大学护理医生格林哈尔博士（Trish Greenhalgh）表示：“没有任何确凿证据表明SARS-CoV-2主要通过空气中的呼吸液滴传播，但绝对没有证据证明这不是传播途径。“
对于新冠病毒是否能通过空气传播没有定论，而专家建议WHO做好“预防措施”，即便没有确信的证据，但依旧做最严谨的防控措施。
“当下我们做的每个决定都面临着不确定性，”格林哈尔博士说，“如果我们决定错误，这将是一场灾难。”
但是，剑桥大学医院的传染病顾问巴巴克·贾维德称，病毒通过空气传播是有可能的，但是还没有证据表明病毒在空气中会停留多久。
目前，239名专家计划将在下周发表期刊文章
新冠病毒是否能通过空气传播没有定论
《新型冠状病毒肺炎防控方案》表明
“在相对封闭的环境中长时间暴露于高浓度气溶胶情况下存在经气溶胶传播的可能”
即使没有确信的证据
我们依然应该保持警惕
做好防控措施
来源：消毒学进展、华医网、消毒前沿
整理：付晗 李文浩
审核：王欣
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