Face coverings and respiratory tract droplet dispersion.
Face coverings and respiratory tract droplet dispersion.
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DOI：
10.1098/rsos.201663
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发表时间：
2020-12
影响因子：
3.5
通讯作者：
Viola IM
中科院分区：
文献类型：
--
作者：
Bandiera L;Pavar G;Pisetta G;Otomo S;Mangano E;Seckl JR;Digard P;Molinari E;Menolascina F;Viola IM
呼吸道飞沫是SARS-CoV-2的主要传播途径，这一原则推动了社会距离指南。有证据表明，戴面罩可以减少病毒传播，但口罩的使用如何影响安全距离参数还缺乏强有力的证据。因此，我们开始量化面部覆盖对呼吸道液滴沉积的影响。我们测试了一个解剖学上逼真的假人头，它可以喷射出荧光水滴和人类志愿者，在说话和咳嗽的条件下，不戴面罩，或者戴着外科口罩或单层棉花面罩。我们使用激光薄片照明和紫外光对那些降落在桌子高度达2米的人的飞行液滴数量进行了量化。对于人类志愿者，呼出的液滴被捕捉到距离口腔5厘米的显微镜载玻片上。无论是模特还是人类，戴上面罩都可以将投射的水滴数量减少不到1000倍。我们估计，一个不戴口罩咳嗽的人站在离咳嗽2米远的地方，接触到的呼吸道飞沫比站在0.5米外戴着基本单层口罩的人多10000多倍。我们的结果表明，面罩在阻止呼吸道飞沫方面显示出一致的效果，因此提供了一个缓和社会距离政策的机会。然而，我们采用的方法主要是检测较大的(非气溶胶)液滴。如果后来确定气雾剂传播是感染的重要驱动因素，那么我们的发现可能高估了面罩的有效性。
Respiratory droplets are the primary transmission route for SARS-CoV-2, a principle which drives social distancing guidelines. Evidence suggests that virus transmission can be reduced by face coverings, but robust evidence for how mask usage might affect safe distancing parameters is lacking. Accordingly, we set out to quantify the effects of face coverings on respiratory tract droplet deposition. We tested an anatomically realistic manikin head which ejected fluorescent droplets of water and human volunteers, in speaking and coughing conditions without a face covering, or with a surgical mask or a single-layer cotton face covering. We quantified the number of droplets in flight using laser sheet illumination and UV-light for those that had landed at table height at up to 2 m. For human volunteers, expiratory droplets were caught on a microscope slide 5 cm from the mouth. Whether manikin or human, wearing a face covering decreased the number of projected droplets by less than 1000-fold. We estimated that a person standing 2 m from someone coughing without a mask is exposed to over 10 000 times more respiratory droplets than from someone standing 0.5 m away wearing a basic single-layer mask. Our results indicate that face coverings show consistent efficacy at blocking respiratory droplets and thus provide an opportunity to moderate social distancing policies. However, the methodologies we employed mostly detect larger (non-aerosol) sized droplets. If the aerosol transmission is later determined to be a significant driver of infection, then our findings may overestimate the effectiveness of face coverings.