无症状感染者正常说话在传播冠状病毒中究竟有多严重？

根据气溶胶科学家的说法，无症状但感染了冠状病毒的人正常说话可能会产生足够的气溶胶颗粒来传播感染。虽然目前还不知道这对COVID-19的传播有多重要，但它强调了严格的社会疏远措施的必要性---病毒学家、流行病学家和研究气溶胶和飞沫的工程师们需要共同研究这种和其他呼吸道疾病。

气溶胶是小到可以在空气中穿行的粒子。

美国加州大学戴维斯分校化学工程教授William Ristenpart表示，普通的讲话会从呼吸道微粒中产生大量的气溶胶。Ristenpart是将在《气溶胶科学与技术》杂志上发表的关于这个问题的社论的共同作者。

这些呼吸道颗粒的直径约为一微米，也就是一微米。这太小了，肉眼看不到，但大到可以携带病毒，如流感或SARS-CoV-2等病毒。

有些人的超标者

去年，Ristenpart、研究生Sima Asadi和同事们发表的一篇论文显示，一个人说话的声音越大，发出的粒子就越多，有些人是 "超级发射器"，发出的粒子数量是其他人的10倍。其原因目前还不清楚。在1月发表在PLOS One上的一项后续研究中，他们调查了哪些语音声音与最多的粒子有关。

要计算像SARS-CoV-2这样的病毒如何容易通过飞沫传播，需要不同领域的专业知识。从病毒学来说，研究人员需要知道肺部体液中有多少病毒，它们如何容易形成飞沫，以及需要多少病毒才能开始感染。气溶胶科学家们可以研究液滴一旦被驱逐出去后会传播多远，液滴在房间里受到空气运动的影响，以及由于重力的作用而沉降的速度。

"气溶胶科学界需要站出来，应对COVID-19带来的当前挑战，同时也帮助我们更好地应对未来不可避免的大流行病，"Ristenpart及其同事总结道。

社论中的其他作者包括Asadi；加州大学戴维斯分校机械和航空航天工程系的Anthony Wexler教授；以及西奈山医学院Icahn医学院的Nicole Bouvier。

Aerosols are particles small enough to travel through the air. Ordinary speech creates significant quantities of aerosols from respiratory particles, said William Ristenpart, professor of chemical engineering at UC Davis. Ristenpart is co-author on an editorial about the problem to be published in the journal Aerosol Science and Technology.

These respiratory particles are about one micron, or one micrometer, in diameter. That's too small to see with the naked eye, but large enough to carry viruses such as influenza or SARS-CoV-2.

Some individuals superemitters

Last year, Ristenpart, graduate student Sima Asadi and colleagues published a paper showing that the louder one speaks, the more particles are emitted and that some individuals are "superemitters" who give off up to 10 times as many particles as others. The reasons for this are not yet clear. In a follow-up study published in January in PLOS One, they investigated which speech sounds are associated with the most particles.

Calculating just how easily a virus like SARS-CoV-2 spreads through droplets requires expertise from different fields. From virology, researchers need to know how many viruses are in lung fluids, how easily they form into droplets and how many viruses are needed to start an infection. Aerosol scientists can study how far droplets travel once expelled, how they are affected by air motion in a room and how fast they settle out due to gravity.

"The aerosol science community needs to step up and tackle the current challenge presented by COVID-19, and also help better prepare us for inevitable future pandemics," Ristenpart and colleagues conclude.

Other authors on the editorial are Asadi; Professor Anthony Wexler, UC Davis Department of Mechanical and Aerospace Engineering; and Nicole Bouvier, Icahn School of Medicine at Mount Sinai.

参考文献：

1. Sima Asadi, Nicole Bouvier, Anthony S. Wexler, William D. Ristenpart. The coronavirus pandemic and aerosols: Does COVID-19 transmit via expiratory particles? Aerosol Science and Technology, 2020; 1 DOI: 10.1080/02786826.2020.1749229

2. Sima Asadi, Anthony S. Wexler, Christopher D. Cappa, Santiago Barreda, Nicole M. Bouvier, William D. Ristenpart. Aerosol emission and superemission during human speech increase with voice loudness. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-019-38808-z

3. Sima Asadi, Anthony S. Wexler, Christopher D. Cappa, Santiago Barreda, Nicole M. Bouvier, William D. Ristenpart. Effect of voicing and articulation manner on aerosol particle emission during human speech. PLOS ONE, 2020; 15 (1): e0227699 DOI: 10.1371/journal.pone.0227699

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