国家地理:为了结束这场流行病 我们必须相信科学(3)（在线收听）

Make no mistake: The challenge is huge and unprecedented. If a typical virus is a riddle wrapped in a mystery inside an enigma, the coronavirus known as SARS-CoV-2 is all that and more. It combines contagiousness and lethality in a ferocious mixture that Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases, has called his "worst nightmare." For one thing, when it appeared, no one on Earth had immunity. Second, it's airborne and infects the upper respiratory tract, which means it's readily spewed back into the air where it can drift from person to person. Third, and arguably worst, the virus is most contagious before it causes symptoms, meaning that carriers feel well enough to be up and about precisely when they're most likely to infect us.

毫无疑问，这项挑战既艰巨又史无前例。如果说一种典型的病毒是包裹在谜团中的一个谜，那么这个被称为SARS-CoV-2的冠状病毒更是如此。它结合了传染性和致死性，美国国家过敏症与传染病研究所所长安东尼·福奇称这个凶猛的组合为“最糟的恶梦”。首先，它出现时，世界上没有人具有免疫力。其次，它通过空气传播感染上呼吸道，这表示它很容易再被喷回到空气中，在人与人之间漂移。第三，也可以说是最糟的，这个病毒在引发症状前的传染力最强，意思是携带病毒者感觉身体健康时，恰好是他们最有可能感染我们的时候。

The tricks this virus uses to foil the body's counterattack are diabolically effective. Once it gets inside via the nose or mouth, the coronavirus eludes the first line of immune defense, slides easily into cells, churns out copies of itself by hijacking the cell's machinery, and makes sure those copies work by using a proofreading mechanism that many other viruses don't even have. Its effect is relentless: It can turn a person's lung cells into useless material that looks like ground glass; blow open blood vessels or destroy them with microscopic clots; and gunk up the workings of a kidney, heart, or liver, rendering them too stiff to repair. It can defang the cells that attack invading viruses and then provoke a secondary immune reaction that goes badly haywire, paradoxically causing its own catastrophe. And anyone who comes in close contact with a person already infected is likely -- though no one is sure how likely -- to get infected too.

这种病毒用来阻挡人体反击的招数很有效。新冠病毒一旦经由口鼻进入体内，就会躲过免疫系统的第一道防线，轻易地进入细胞，进行复制，并且利用其他许多病毒都没有的校正机制来确保复制的病毒功能正常。它会将人的肺部细胞转变成毛玻璃状的无用物质，让血管爆开或以微小血块破坏血管，以及造成肾脏、心脏或肝脏功能受损，使它们变得过于硬化而无法修复。它可以削弱攻击入侵病毒的细胞，能引发严重失控的次级免疫反应，矛盾地造成自身体内的灾难。此外，任何与已感染者近距离接触的人也很有可能遭受感染――尽管没人确定可能性有多高。