新冠为何可以致命
More than 1,300 people, almost all in China, have now died from COVID-19 — the newly minted name for the coronavirus disease first identified in Wuhan, China, that has infected more than 55,000 people.
目前约有1300人，因COVID-19病毒而去世了，大部分为中国病例，COVID-19是给中国武汉首先检测到的这种新型冠状病毒最近确定的名字，目前已经有超过55,000人确诊。
Yet according to the World Health Organization, the disease is relatively mild in about 80% of cases, based on preliminary data from China.
根据世界卫生组织的统计，按照之前中国提供的数据，其中80%都是症状较为温和的病例。
What does mild mean?
症状温和是什么意思呢？
And how does this disease turn fatal?
这种疾病又是如何变得致命的呢？
The first symptoms of COVID-19 are pretty common with respiratory illnesses — fever, a dry cough and shortness of breath, says Dr. Carlos del Rio, a professor of medicine and global health at Emory University who has consulted with colleagues treating coronavirus patients in China and Germany.
COVID-19最初的症状跟普通的肺病很像—包括发烧，喉咙干涩，呼吸急促等，卡洛斯·德尔·瑞奥有医生说道，他是埃默里大学医学与全球健康教授，他和同事一起在中国和德国的新冠病患治疗方面提供咨询。
"Some people also get a headache, sore throat," he says.
“有些人还会出现头疼，喉咙酸痛等，”他说道。
Fatigue has also been reported — and less commonly, diarrhea.
也有病患出现乏力—少数患者还会出现腹泻症状。
It may feel as if you have a cold.
感觉就像你得了感冒一样。
Or you may feel that flu-like feeling of being hit by a train.
又或者感觉到像那种流感来袭时被击倒的感觉。
Doctors say these patients with milder symptoms should check in with their physician to make sure their symptoms don't progress to something more serious, but they don't require major medical intervention.
医生说，出现这些轻微症状的患者，可以跟他们的医生进行确认，以免这些症状发展的更为严重，但他们并不需要更复杂医疗干预。
But the new coronavirus attacks the lungs, and in about 20% of patients, infections can get more serious.
不过，这种新冠病毒攻击的是肺部，在20%左右的病患体内感染，可能会更严重。
As the virus enters lung cells, it starts to replicate, destroying the cells, explains Dr. Yoko Furuya, an infectious disease specialist at Columbia University Irving Medical Center.
随着这种病毒进入肺部细胞，它就会开始复制，并破坏细胞，古屋洋子解释道，她是哥伦比亚大学艾尔文医学中心的传染病学专家。
"Because our body senses all of those viruses as basically foreign invaders, that triggers our immune system to sweep in and try to contain and control the virus and stop it from making more and more copies of itself," she says.
“这是因为我们的身体会感测到这些病毒作为一种外来入侵者，然后就会刺激我们的免疫系统进入肺部，试图控制病毒，阻止病毒的进一步复制。”她说道。
But Furuya says that this immune system response to this invader can also destroy lung tissue and cause inflammation.
但古屋说这种对外部入侵者的免疫应答也可能会损伤肺部组织带来炎症。
The end result can be pneumonia.
最终结果就会造成肺炎。
That means the air sacs in the lungs become inflamed and filled with fluid, making it harder to breathe.
这就意味着肺部当中的肺泡会开始发炎，并被液体填充，导致呼吸困难。
Del Rio says that these symptoms can also make it harder for the lungs to get oxygen to your blood, potentially triggering a cascade of problems.
德尔·瑞奥说这些症状还可能会使得肺部很难汲取氧气供给血液，从而导致一系列的其他问题。
"The lack of oxygen leads to more inflammation, more problems in the body. Organs need oxygen to function, right? So when you don't have oxygen there, then your liver dies and your kidney dies," he says.
“氧气的缺乏会带来更多的炎症，以及身体中的更多问题。我们的器官都需要氧气才能够运行，对吧？所以如果缺氧了，肝脏就会坏掉，肾脏也会坏掉，”他说道。
That's what seems to be happening in the most severe cases.
那些最严重的病患可能面临的就是这样的状况。
About 3% to 5% of patients end up in intensive care, according to the WHO.
根据世界卫生组织数据，大约3%到5%的病患最后进了重症监护室。
And many hospitalized patients require supplemental oxygen.
而很多住院的病患都需要额外的氧气供应。
In extreme cases, they need mechanical ventilation — including the use of a sophisticated technology known as ECMO (extracorporeal membrane oxygenation), which basically acts as the patient's lungs, adding oxygen to their blood and removing carbon dioxide.
在最严重的病患中，他们需要一种呼吸机—包括一种复杂的叫做体外膜氧合的技术，这种机器就好比是病人的肺一样，可以给他们的血液补充氧气，并去除二氧化碳。
The technology "allows us to save more severe patients," Dr. Sylvie Briand, director of the WHO's pandemic and epidemic diseases department, said at a press conference Monday.
“这种技术让我们拯救了更多的危重病患，”塞尔维·布兰德医生说，他是世界卫生组织传染疾病部门的主任，这是他在周一的一次新闻发布会上说的。
Many of the more serious cases have been in people who are middle-aged and elderly — Furuya notes that our immune system gets weaker as we age.
很多这些严重的症状都是那些中年或者老年患者出现的—古屋医生提醒到随着年龄的增长，我们的免疫系统会变得更弱。
She says for long-term smokers, it could be even worse because their airways and lungs are more vulnerable.
她说，对于那些长期抽烟的患者来说，情形还会更严重，因为他们的气道和肺部更脆弱。
People with other underlying medical conditions, such as heart disease, diabetes or chronic lung disease, have also proved most vulnerable.
那些伴有其他的健康问题，例如心脏病，糖尿病或者慢性肺炎的人也会更加脆弱。
Furuya says those kinds of conditions can make it harder for the body to recover from infections.
古屋医生说，这样的情形会让身体更加难以从炎症中恢复。
"Of course, you have outliers — people who are young and otherwise previously healthy who are dying," Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.
“当然，也有例外，那些年轻之前很健康的人们也有出现死亡的病例。”安东尼·福西医生说道，他是过敏和传染病学国家中心的主任。
"But if you look at the vast majority of the people who have serious disease and who will ultimately die, they are in that group that are either elderly and/or have underlying conditions."
“但如果从大部分那些危重或者死亡病患的情况来看，他们都属于那种年龄较长，或者伴有其他疾病的类型。”
The WHO has said most deaths so far appear to be from multi-organ failure and has calculated the case fatality rate at about 2% or less, based on earlier data from China.
根据中国早前提供的数据，世界卫生组织称，目前大部分的死亡病例都是因为多器官衰竭，并计算出死亡率目前大概是2%。
However, infectious disease experts note that it's hard to know the true numbers at this point in the epidemic.
不过，传染病专家提醒的目前很难计算出这种疾病死亡率的真正数字。
But del Rio notes that it's not just COVID-19 that can bring on multi-organ failure.
而德尔·瑞奥医生提醒的，并不是只有COVID-19才能够导致多器官衰竭。
Just last month, he saw the same thing in a previously healthy flu patient in the U.S. who had not gotten a flu shot.
就在上个月他就遇到了一个之前接种过流感疫苗的患者，在患上流感后也出现了同样的症状。
"He went in to a doctor. They said, 'You have the flu — don't worry.' He went home. Two days later, he was in the ER. Five days later, he was very sick and in the ICU" with organ failure, del Rio says.
“他当时去看医生，医生说，'你得的是流感—别担心'然后他就回家了。两天后他就进了急诊室，五天之后，他因为器官衰竭已经进了重症监护。”德尔·瑞奥医生说道。
While it's possible for patients who reach this stage to survive, recovery can take many weeks or months.
尽管到了这一阶段的病患有可能存活，但是要恢复起来，需要数周甚至数月的时间。
In fact, many infectious disease experts have been making comparisons between this new coronavirus and the flu and common cold, because it appears to be highly transmissible.
事实上，很多传染病学专家都在对比这次的新冠病毒以及流感和普通感冒病毒，因为它们似乎很容易被混淆。
"What this is acting like — it's spreading much more rapidly than SARS [severe acute respiratory syndrome], the other coronavirus, but the fatality rate is much less," Fauci told us.
“这次的病毒传播的速度比非典和其他的冠状病毒更快，但死亡率更低。”福西告诉我们说。
"It's acting much more like a really bad influenza."
“它的情形更像是严重的流感。”
What experts fear is that, like the flu, COVID-19 will keep coming back year after year.
专家们担心的事情是，像流感一样，COVID-19有可能会年复一年地卷土重来。
问题
文中提到老年人和青年人相比，哪种人群对这次的病毒更脆弱呢？
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