2020年经济学人 疫情与口罩(1)（在线收听）

"This is a, I would say, senseless dividing line," said Doug Burgum, governor of North Dakota,

“我认为，这是一条毫无意义的分界线”，美国北达科他州道格·柏格姆说，

his voice catching as he talked of the rows that have broken out in his state over the wearing of face-coverings.

当他谈到自己所在的州因为戴口罩而引发争吵时，他的声音很有感染力。

There are similar spats elsewhere in America, for masks have become the latest aspect of the culture war that has emerged there over how to deal with covid-19.

美国其他州也发生了类似的争吵，因为口罩已经成为因如何应对covid-19而爆发的文化战争中的最新议点。

Some shops refuse entry to maskwearers and Mike DeWine, the governor of Ohio,

一些商店拒绝让戴口罩的人进店，俄亥俄州的州长麦克·德维尼

has rescinded an order requiring people to wear them, saying that he "went too far".

已经取消了要求人们佩戴口罩的要求，称这么做“太过了”。

Elsewhere in the world, by contrast, there is increasing acceptance that mask-wearing is a good thing.

相比之下，世界其他地方，越来越多的人接受戴口罩是件好事。

On May 5th, for example, the Royal Society, Britain's top science academy,

例如，5月5日，英国顶尖科学学院，英国皇家学会总结称，

concluded that masks "could be an important tool for managing community transmission".

口罩“可以成为管理社区传播的一个重要工具”。

This is not so much because they protect the wearer--the normal reason people may put them on in times of pestilence--

与其说是因为口罩保护了佩戴者——人们在疫情期间佩戴口罩的普遍原因——

but rather because they stop the wearer infecting others.

还不如说是因为它们能够防止佩戴者感染其他人。

In this context covid-19's particular peculiarlty--that people who test positive for it often do not have symptoms--is important.

在这个背景下，covid-19的特性——检测呈阳性的人不一定会出现症状——很重要。

Research published last month in Nature Medicine, by Xi He of Guangzhou Medical University and Eric Lau of Hong Kong University,

上个月，由广州医科大学的Xi He以及香港大学的Eric Lau发表于《自然医学》杂志的研究表明，

suggests that 44% of cases are caused by transmission from people without symptoms at the time of transmission.

44%的病例都是由无症状患者传播引起的。

Those who do have symptoms should not, of course, be out and about at all. In their case masks are irrelevant.

当然那些有症状的患者根本就不应该出门走动。对他们来说，口罩是无关紧要的。

But to break the chain, it behoves even the symptomless to assume that they might be infected.

但是为了打破这个链条，即使没有任何症状的人也应该假设他们可能被感染了。

Covid-19 is transmitted, above all, by virus-laden droplets of spit. Experiments show that face-coverings as simple as tea-towels are effective.

Covid-19主要通过携带病毒的唾液传播。实验表明像茶巾一样简单的面部遮盖物是有效的。

One study found that a tea-towel worn around the face captured 60% of droplets.

一项研究发现，戴在脸上的茶巾可以吸附60%的飞沫。

At 75%, a surgical mask did better, but not overwhelmingly so.

外科口罩的效果更好，能吸附75%的飞沫，但也不是绝对如此。

Governments are beginning to take this on board. As part of the loosening their lockdown,

各国政府开始接受这一点。作为解除封锁的一部分，

the Dutch are required to wear face-coverings on public transport--but not ones of medical grade,

荷兰人被要求在乘坐公共交通时佩戴口罩——但不是医用级别的口罩，

which should be reserved for professionals. This encourages people to make their own.

这类口罩应该留给专业人士。这鼓励了人们自制口罩。

Neither laboratory studies nor the data on asymptomatic transmission provide watertight evidence of the efficacy of masks.

无论是实验室研究还是关于无症状传播的数据都不能提供无懈可击的证据证明口罩的有效性。

That would need randomised controlled trials, in which one group wore masks and the other did not.

这需要进行随机对照实验，一组戴口罩，另一组不戴。

This would be ethically tricky, since it might condemn one of the groups to a higher death rate.

这将成为一个棘手的道德问题，因为这可能会使其中一个群体的死亡率更高。

Hamsters, which are susceptible to covid-19, are the next best thing to people.

仓鼠很容易感染covid-19，它们是仅次于人类的最好选择。

So researchers at Hong Kong University put cages of healthy hamsters next to cages of infected ones,

所以香港大学的研究人员把装有健康仓鼠的笼子和装有感染仓鼠的笼子放在一起，

with a fan in between drawing air from the infected to the healthy cage. They sometimes also placed a stretched-out face mask in the air stream.

中间有一台风扇，将感染组的空气抽向健康组。他们有时也会在气流中放置一个拉伸的面罩。

With no interposed mask, two-thirds of the healthy hamsters were infected within a week.

在没有插入面罩的情况下，三分之二的健康仓鼠在一周内被感染。

With a mask interposed close to the healthy hamsters (the equivalent of a healthy person wearing a mask), one-third were.

在靠近健康仓鼠笼子的地方插入面罩（相当于一个健康人类佩戴一个口罩），仅有三分之一的仓鼠被感染。

With the mask close to the infected hamsters, only a sixth were.

在靠近感染仓鼠笼子的附近插入面罩，仅有六分之一的仓鼠感染。