Q. How effective are antimicrobial “courtesy masks” at preventing the spread of contagious airborne illnesses?

问：抗菌“礼貌口罩”在预防空气传播疾病方面效果如何?

A. The best evidence suggests that, when sick, wearing a mask can help to protect others from getting sick. And when well, wearing a mask around those who are sick will probably decrease your own chances of becoming infected. But the masks are far from foolproof.

答：最确凿的证据表明，生病时戴口罩有助于避免其他人患病。健康者在患者周围时戴口罩很可能会降低被感染的几率。但口罩绝非万无一失。

Courtesy masks, or what we doctors refer to as surgical masks, were introduced into the operating room in the late 1800s. They quickly became popular among a public eager to protect itself against the influenza pandemic of 1918.

礼貌口罩，也就是我们医生所说的医用口罩，是在19世纪晚期被引入手术室的。在1918年流感大流行期间，公众渴望保护自己免于患上流感，所以这种口罩很快流行起来。

A century later, the advent of modern molecular techniques confirmed that surgical masks can indeed provide good protection against flu. In a 2013 study, researchers counted the number of virus particles in the air around patients with flu. They found that surgical masks decreased the exhalation of large viral droplets 25-fold. The masks were, however, less effective against the fine viral droplets that can remain suspended in the air longer and are therefore more infectious, cutting them by 2.8 times.

一个世纪后，现代分子技术证实了医用口罩确实能够很好地预防流感。在2013年的一项研究中，研究人员统计了流感患者周围空气中病毒颗粒的数量。他们发现，医用口罩可将大病毒飞沫的吸入量减少至1/25。不过，这种口罩抵挡在空气中悬浮时间更长、因此更具传染性的细小病毒飞沫的效果较差，只能将它们的吸入量减少2.8倍。

Surgical masks also afford fairly good protection for the worried well. In an oft-cited study of 446 nurses, researchers found surgical masks were as good, or nearly as good, at protecting the wearer against flu as respirators, a somewhat more high-tech, masklike device used in hospitals.

医用口罩也能很好地保护担心患病的健康人士。在一项经常被引用的对446名护士的研究中，研究人员发现，医用口罩在保护佩戴者免于感染流感方面几乎和防护面罩一样有效，后者是医院使用的一种技术含量更高的面具式设备。

The work of Australian investigators provides further support for the value of the simple surgical mask. They estimate that in a home setting, wearing a surgical mask decreases a well person’s risk of getting sick by 60 percent to 80 percent.

澳大利亚调查人员的研究进一步巩固了简单的医用口罩的价值。据他们估计，在居家环境中，佩戴医用口罩能将一个健康人患病的风险降低60%至80%。

Unfortunately, most people fail to wear a mask faithfully enough to achieve this degree of protection, and the Centers for Disease Control and Prevention remains equivocal about the use of masks outside of health care settings. “No recommendation can be made at this time for mask use in the community by asymptomatic persons, including those at high risk for complications, to prevent exposure to influenza viruses,” the agency concludes on its website.

不幸的是，大多数人佩戴口罩不够坚持，不足以实现这种程度的保护，而美国疾病控制和预防中心(Centers for Disease Control and Prevention)对在医疗场合之外佩戴口罩的态度依然模棱两可。该机构在自己的网站上给出的结论是：“目前，对于无症状人群，包括并发症高危人群，在社区中佩戴口罩预防流感病毒方面，我们并不能给出任何建议。”

If you don’t have a mask, or don’t want to wear one, standing at least six feet from an infected person will increase your chances for staying healthy. The air surrounding sick people, even if they aren’t coughing or sneezing, is loaded with small infectious aerosolized particles, and the farther you are from them, the better.

如果你没有口罩，或者不想戴口罩，那么，站在离感染者至少6英尺的地方会增加你保持健康的几率。即使患者没在咳嗽或打喷嚏，他们周围也充满具有传染性的雾状微小颗粒，离它们越远越好。

Washing your hands frequently, of course, is also critical for staying healthy, since touching infected fingers to the eyes, nose or mouth can transmit infection.

当然，经常洗手对保持健康也很重要，因为受到污染的手指触摸眼睛、鼻子或口腔也会导致感染。