是的，戴口罩有帮助。这是为什么

是的，戴口罩有帮助。这是为什么

Mask wearing has become a topic of fierce debate.

戴口罩已经成为了激烈争论的话题。

Take, for example, an analysis of 172 studies that looked at various interventions to prevent the transmission of COVID-19, SARS and MERS from an infected person to people close to them. The analysis, which was published in The Lancet on June 1, found that mask wearing significantly reduces the risk of viral transmission.

以一项对172项研究的分析为例，该研究考察了防止COVID-19、SARS和中东呼吸综合征(MERS)从感染者向其身边人传播的各种干预措施。6月1日发表在《柳叶刀》上的这项分析发现，戴口罩可以显著降低病毒传播的风险。

"What this evidence supports is that, if there is a policy around using face masks in place, it does actually come with a fairly large effect," says study co-author Holger Schünemann, an epidemiologist at McMaster University.

麦克马斯特大学的流行病学家、研究合著者霍尔格·舒内曼说：“这些证据支持的是，如果有一项关于使用口罩的政策出台，它确实会产生相当大的效果。”

Now, most of the studies in the analysis looked at face mask use in health care, not community, settings. And they were observational, not the gold standard of science, a randomized controlled trial, which would be "very unethical in a pandemic," says Jeffrey Shaman, an epidemiologist at Columbia University.

现在，大多数分析中的研究关注的是口罩在卫生保健中的使用，而不是社区环境。而且它们是观察性的，而不是科学的黄金标准，是随机对照试验。哥伦比亚大学的流行病学家詹佛瑞·沙曼说，这种试验“在大流行中非常不道德”。

Still, he says the fact that there is a benefit from masks is clear.

不过，他说，口罩的好处是显而易见的。

"I personally think that face masks are a key component of the non-pharmaceutical arsenal we have to combat COVID-19," says Shaman.

“我个人认为，口罩是我们抗击COVID-19的非药物武器的一个关键组成部分，”沙曼说。

It's understandable if some people remain skeptical. But that changed as it became clear that infected people can spread the coronavirus before they even show symptoms of COVID-19 or even if they never show symptoms.

有些人对此持怀疑态度是可以理解的。但情况发生了变化，因为人们清楚地认识到，感染者甚至在出现COVID-19症状之前，或者即使从未出现症状，也可以传播冠状病毒。

Researchers emphasize there are two main reasons to wear masks. There's some evidence of protection for the wearer, but the stronger evidence is that masks protect others from catching an infection from the person wearing the mask. And infected people can spread the virus just by talking.

研究人员强调，戴口罩有两个主要原因。有一些证据表明口罩对佩戴者有保护作用，但更有力的证据是，口罩可以保护其他人免受戴口罩者的感染。被感染的人可以仅通过交谈传播病毒。

"If you're talking, when things are coming out of your mouth, they're coming out fast," says Linsey Marr, a researcher at Virginia Tech who studies the airborne transmission of viruses. " I think even a low-quality mask can block a lot of those droplets."

弗吉尼亚理工大学研究病毒通过空气传播的研究员林夕·马尔说:“如果你在说话，当东西从你嘴里出来的时候，它们出来的速度很快。”“我认为即使是一个低质量的口罩也能阻挡很多飞沫。”

Marr points to a study published in Nature Medicine in April that looked at people infected with the flu and seasonal coronaviruses. It found that even loose-fitting surgical masks blocked almost all the contagious droplets the wearers breathed out and even also some infectious aerosols — tiny particles that can linger in the air.

马尔指出，4月份发表在《自然医学》上的一项研究对感染流感和季节性冠状病毒的人进行了研究。研究发现，即使是宽松的医用口罩，也能阻挡佩戴者呼出的几乎所有传染性飞沫，甚至还能阻挡一些传染性气溶胶——能滞留在空气中的微小颗粒。