2021年经济学人 关于口罩你不知道的秘密

Face-masks and covid-19

口罩和新冠

Helpful humidity

有用的湿度

As well as filtering air, face-masks may boost the immune system

口罩除了过滤空气，还可以增强免疫系统

Face-masks help reduce the spread of SARS-COV-2, the virus that causes covid-19. Several studies have reported the more surprising finding that, even if wearers do become infected, their disease is usually milder. Now Joseph Courtney and Ad Bax, a pair of researchers at the National Institutes of Health in Bethesda, Maryland, think they may have worked out why. As they report in the Biophysical Journal, it comes down to humidity, the immune system, and the protective powers of mucus.

口罩有助于减少导致新冠的SARS-COV-2(新型冠状病毒)的传播。一些研究报告了更为惊人的发现：即使口罩佩戴者被感染了，他们的症状通常也比较轻。目前，马里兰州贝塞斯达国家卫生研究院的两位研究员约瑟夫·考特尼和艾德·巴克斯认为他们可能已经找到了原因。他们在《生物物理学杂志》上发表的报告称，这归结为湿度、免疫系统和黏液的保护能力。

At first glance, there may not seem much of a mystery to unravel¹. Masks cut the number of infectious particles entering the nose and mouth. One might expect, therefore, that severe disease would be less likely. But it is not so. One vital factor which predicts disease severity is how far viral particles make it into a person's lungs. Cheap cotton face-masks struggle to block the smallest aerosols², which are the most likely to penetrate³ deeply. Dr Courtney and Dr Bax wondered if something else might explain their protective effect.

乍一看似乎没有什么神秘的事物需要揭开。口罩可以减少进入口鼻的传染性颗粒，因此人们可能会认为感染严重疾病的可能性会降低。但事实并非如此。预测疾病严重程度的一个重要因素是病毒颗粒进入人体肺部的距离。廉价的棉质口罩很难阻挡最小的悬浮微粒，而这些悬浮微粒最有可能渗透到深处。考特尼博士和巴克斯博士想探究是否有其他原因可以解释它们的保护作用。

One of the body's first lines of defence against airborne pathogens is known as the "mucociliary clearance⁴ mechanism⁵". Sticky mucus in the nose and respiratory tract⁶ snares⁷ viruses and bacteria. Little hairs known as cilia push the mucus into the throat. From there it is swallowed and potent⁸ stomach acids destroy the invaders⁹. But this mechanism relies on the relevant body parts staying moist.

人体抵抗空气传播病原体的第一道防线被称为“黏液纤毛清除机制”。鼻子和呼吸道里黏黏的粘液会吸引病毒和细菌，被称为纤毛的细小毛发会将粘液推入喉咙，粘液在喉咙处被吞下，之后强有力的胃酸摧毁入侵者。但这一机制依赖于一点：相关身体部位要保持湿润状态。

That is harder in winter, for as air gets colder, its capacity to hold waterfalls. Lower humidity tends to dry out the respiratory tract. This is one reason why many upper-respiratory viruses, such as influenza¹⁰, flourish in the winter.

在冬天更难，因为随着空气变冷，它容纳水分的能力会减弱。湿度较低会使呼吸道变得干燥。这就是许多上呼吸道病毒(如流感病毒)在冬季肆虐的原因之一。

Dr Courtney and Dr Bax speculated that masks may help keep things damp. They reasoned that, as a person exhales¹¹, water vapour would condense on the inside of a mask. Then, upon inhalation, dry air passing through the mask would collect the deposited water and bring it back into the respiratory tract and lungs. That could be handing a mask-wearer's immune system a significant advantage.

考特尼博士和巴克斯博士推测，口罩可能具备保持湿润的功效。他们推断，当一个人呼气时水蒸气会在口罩内部凝结，被吸入后通过口罩的干燥空气会收集积水并将其带回呼吸道和肺部。这可能会给戴口罩者的免疫系统带来很大的好处。

Keen to test their idea, the researchers checked several masks at 37°C, 22°C and 8°C. They breathed into a sealed box packed with sensitive instruments, and worked out humidity levels in their upper respiratory tracts¹². They found that, although all masks increased humidity levels to some extent, the heavy cotton mask did best of all. In the hottest room it boosted the relative humidity of inspired air by over 50%, compared with breathing without a mask. In the cold room, that number rose to 300%. (The other masks recorded figures of between 150% and 225%.) That suggests that, besides filtering out at least some of the viral particles floating about in the air, masks help keep a person's snot levels healthily high.

为了验证他们的想法，研究人员在37°C、22°C和8°C的温度下检验了几种口罩。他们向一个密封的盒子里呼气，盒子里装满了敏感的仪器，然后计算出他们上呼吸道的湿度。他们发现，虽然所有的口罩都在一定程度上增加了湿度，但厚重的棉质口罩效果最好。在最热的房间里，戴棉质口罩呼吸与不戴口罩呼吸相比，它使吸入空气的相对湿度提高了50%以上。在寒冷的房间里这一数字上升到了300%。(其他口罩的记录数字在150%至225%之间。)这表明，口罩除了能过滤掉空气中漂浮的部分病毒颗粒外，还能让人的鼻涕保持在非常高的健康水平。

1 unravel   

v.弄清楚（秘密）；拆开，解开，松开

参考例句：

• He was good with his hands and could unravel a knot or untangle yarn that others wouldn't even attempt.他的手很灵巧，其他人甚至都不敢尝试的一些难解的绳结或缠在一起的纱线，他都能解开。
• This is the attitude that led him to unravel a mystery that long puzzled Chinese historians.正是这种态度使他解决了长期以来使中国历史学家们大惑不解的谜。

2 aerosols   

n.气溶胶( aerosol的名词复数 )；喷雾剂；（气体中的）浮粒；喷雾器

参考例句：

• Aerosols are present throughout the atmosphere. 气溶胶存在于整个大气层。 来自辞典例句
• Deodorants are available as aerosols or roll-ons. 除臭剂有喷雾装或滚抹装。 来自辞典例句

3 penetrate   

v.透(渗)入；刺入，刺穿；洞察，了解

参考例句：

• Western ideas penetrate slowly through the East.西方观念逐渐传入东方。
• The sunshine could not penetrate where the trees were thickest.阳光不能透入树木最浓密的地方。

4 clearance   

n.净空；许可(证)；清算；清除，清理

参考例句：

• There was a clearance of only ten centimetres between the two walls.两堵墙之间只有十厘米的空隙。
• The ship sailed as soon as it got clearance. 那艘船一办好离港手续立刻启航了。

5 mechanism   

n.机械装置；机构，结构

参考例句：

• The bones and muscles are parts of the mechanism of the body.骨骼和肌肉是人体的组成部件。
• The mechanism of the machine is very complicated.这台机器的结构是非常复杂的。

6 tract   

n.传单，小册子，大片(土地或森林)

参考例句：

• He owns a large tract of forest.他拥有一大片森林。
• He wrote a tract on this subject.他曾对此写了一篇短文。

7 snares   

n.陷阱( snare的名词复数 )；圈套；诱人遭受失败（丢脸、损失等）的东西；诱惑物v.用罗网捕捉，诱陷，陷害( snare的第三人称单数 )

参考例句：

• He shoots rabbits and he sets snares for them. 他射杀兔子，也安放陷阱。 来自《简明英汉词典》
• I am myself fallen unawares into the snares of death. 我自己不知不觉跌进了死神的陷阱。 来自辞典例句

8 potent   

adj.强有力的，有权势的；有效力的

参考例句：

• The medicine had a potent effect on your disease.这药物对你的病疗效很大。
• We must account of his potent influence.我们必须考虑他的强有力的影响。

9 invaders   

入侵者，侵略者，侵入物( invader的名词复数 )

参考例句：

• They prepared to repel the invaders. 他们准备赶走侵略军。
• The family has traced its ancestry to the Norman invaders. 这个家族将自己的世系追溯到诺曼征服者。

10 influenza   

n.流行性感冒，流感

参考例句：

• They took steps to prevent the spread of influenza.他们采取措施
• Influenza is an infectious disease.流感是一种传染病。

11 exhales   

v.呼出，发散出( exhale的第三人称单数 )；吐出（肺中的空气、烟等），呼气

参考例句：

• He shivers, exhales, gets the ball and races back to his friends. 他浑身一颤，舒了口气，捡起球，跑回到他的朋友们那里。 来自互联网
• A smoker exhales in a pub in Richmond, London. 一名吸菸者在伦敦瑞旗蒙一家酒吧吞云吐雾。 来自互联网

12 tracts   

大片土地( tract的名词复数 )； 地带； （体内的）道； （尤指宣扬宗教、伦理或政治的）短文

参考例句：

• vast tracts of forest 大片大片的森林
• There are tracts of desert in Australia. 澳大利亚有大片沙漠。