比SARS更致命：蝙蝠病毒MERS是如何成为人类杀手的
Erika Fry | 2014-09-01 04:00
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[译文]
“传染”系列文章：
【传染之一】比SARS更致命：蝙蝠病毒MERS是如何成为人类杀手的
【传染之五】从贾斯汀•比伯到数据学家，Twitter何以成为一门显学
By all appearances, the camel had a cold. One of nine camels kept in a barn outside Jeddah, Saudi Arabia, the animal was sick and expelling nasal discharge. The camel’s owner did what he could to help, swabbing his own finger in vapor rub and applying it inside the dromedary’s nose.
Seven days later, the owner—age 43 or 44, depending on the source—began feeling tired and developed a runny nose and cough. Five days after that, he found it harder to catch his breath. Three days later he was admitted into the ICU with severe shortness of breath. Fifteen days later, the man was dead. That was last November.
The camel recovered.
As it turns out, what the runny-nosed animal had wasn’t a cold at all. It was MERS, or Middle Eastern respiratory syndrome, the same virus that would kill its owner—likely, MERS’ 72nd reported victim—some four and a half weeks later.
Relatively common and benign in camels, MERS—which belongs to the family of coronaviruses that includes both SARS and the common cold—first emerged as a threat to humans in September 2012. Spiky in shape and only a few nanometers big, the virus has been making its slow, but often-deadly spread around the globe ever since: according to latest lab-confirmed stats from the World Health Organization, MERS-CoVhas now infected at least 837 people and killed 291 of them.
Most of these cases have occurred on the Arabian Peninsula (Saudi Arabia has reported more than the WHO with 723 infections and 299 deaths), though patients have also turned up far from Jeddah—in more than 20 countries, including locales as far away from the Middle East as France, Malaysia, and even Munster, Indiana. (In late April, a U.S. resident, who had been working at a Saudi medical facility, walked into the E.R. at Munster’s Community Hospital—and, in a remarkable example of good hospital procedure and care, was successfully treated and later released.)
This spring, infections rose at an especially alarming rate. In April, the global number of new MERS cases reported surpassed the total reported in the previous two years, according to the European Centre for Disease Prevention and Control, Europe’s counterpart to the U.S. Centers for Disease Control and Prevention. And in early June—shortly after Saudi Arabia’s health minister was sacked—that country’s Ministry of Health announced the count was even higher than thought, revealing that the previous minster had missed 113 cases (92 of them now deceased).
Ebola may have the world terrified these days, but earlier this year, as cases spiked and jumped continents, MERS-CoV was the virus that had the globe’s public health officials on edge. Its spread has slowed down this summer, but the pathogen hasn’t gone away—nor, worryingly, have epidemiologists completely figured it out.
The strange power and unpredictable nature of contagion, whether it be the spread of disease or a whimsical social fad, has long fascinated scientific and creative minds alike. And at Fortune, we’ve been intrigued by it too. In this series of essays, my colleagues and I have set out to trace a wide range of “outbreaks”—from that of the MERS-CoV to less deadly spreads like M&A rumors, market panics, book sales, and that modern phenomenon known as the “selfie“—with the hopes of better understanding them. Some contagions are more easily explained by science than others, and one would expect MERS, like Ebola, to fall into the category of the scientifically explicable.
从外表的各种迹象来看，这头骆驼是感冒了。沙特阿拉伯吉达一个谷仓共有九头骆驼，这是其中之一。它病了，不断地流鼻涕。骆驼的主人已经倾尽所能，他将手指蒙上蒸汽熏过的湿布，伸进骆驼的鼻孔里擦拭。
7天后，骆驼的主人（据消息源说，年龄是43岁或44岁）开始感觉疲倦，流鼻涕并且咳嗽不止。随后5天，他发现自己越来越喘不过气。3天后，他因为严重的呼吸短促被送进重症护理病房（ICU），并于15天后死亡。这件事发生在去年11月。
而骆驼康复了。
事实证明，那头流鼻涕的骆驼根本没有感冒，而是患上了MERS，即中东呼吸系统综合征（Middle East Respiratory Syndrome）。也正是这个病毒，在4个半星期后夺去了它主人的生命。这或许是第72例记录在案的MERS受害者。
MERS病毒在骆驼身上相对普遍，而且是良性的。它与重症急性呼吸综合征（SARS）病毒和引起普通感冒的病毒同属于冠状病毒，并于2012年9月首次威胁到人类的生命。从那时起，这种形似钉子，只有几纳米长的致命病毒，就慢慢地开始在全球扩散：根据世界卫生组织（World Health Organization）发布的已经过实验室确认的数据，MERS病毒已经至少感染了837人，造成其中291人死亡。
大多数病例发生在阿拉伯半岛（沙特阿拉伯报告的感染死亡数比世界卫生组织还要多，有723例感染，299例死亡），不过也有病人出现在远离吉达的20多个国家，包括远离中东的法国、马来西亚，甚至美国印第安纳州明斯特市。（去年4月，一位曾经在沙特阿拉伯医疗机构工作过的美国居民，走进了明斯特的社区医院急诊室。由于医院处理得当，看护有方，这位病人最终痊愈出院。）
今年春天，感染者的增速尤其惊人。根据欧洲疾病控制与预防中心（European Centers for Disease Control and Prevention，其作用相当于美国疾病控制与预防中心）的数据，单单今年4月报告的全球新增MERS病例，就超过了前两年病例数的总和。而在沙特阿拉伯卫生部长下台不久后的6月初，该国卫生部就宣布病例数甚至比之前想象的更高，并表示前任部长至少漏报了113起病例（其中有92人现已死亡）。
埃博拉病毒（Ebola）近来让全球陷于恐慌之中，不过在今年早些时候，病例在各大洲激增的MERS病毒才是让全球卫生部门的官员最为头疼的。今年夏天，病情的蔓延趋势有所减缓，但病原体并未消失，更让人担忧的是，流行病学专家至今还没有把它彻底搞清。
无论是疾病还是怪诞的社会潮流，传染所具有的神奇魔力和不可预知性，一直让热爱科学和创新的人群深深着迷。在《财富》（Fortune）工作的我们也不例外。在这一系列短文中，我和我的同事将追寻各种不同的“突然蔓延”——从MERS病毒到不那么致命的并购传言、市场恐慌、图书销售以及当代“自拍”现象——希望更好地了解它们。一些趋势的蔓延更容易用科学来解释。人们也认为MERS病毒能够像埃博拉病毒一样，属于科学能够解释的那一类。
Yet what makes MERS so scary to some, is just how much about it remains in the realm of mystery—starting with something critical: how exactly humans become infected and how they pass the virus on to others. There are clues with MERS—the sick camels, for one—but currently, bats, camels, hospitals, unprotected health care workers, unclean surfaces and politics have all shouldered a bit of the speculative blame. One Australian epidemiologist, citing “paradoxes” involved in MERS’ spread, recently even suggested that bioterrorism may have a role.
Meanwhile, two years since MERS was first discovered in humans—and now in the shadow of Ebola—the tally of patients and fatalities continues to climb. Saudi Arabia reported two new cases just last week.
The WHO has convened six Emergency Committee meetings on MERS, which by the health organization’s latest reckoning kills 35% of its victims. But while MERS has earned the carefully trained eye of the world’s medical community, it has not yet been deemed a “public health emergency of international concern.”
Even so, it has made for an unsettling state of affairs given the number of pilgrims traveling to Saudi Arabia this summer and fall. Ramadan, the peak season to perform the Umrah (a religious journey to Mecca that many Muslims make), drew more than 6 million to the country in July. And in October, many more people from all over the world will crowd into Islam’s holy city for the Hajj—a pilgrimage to Mecca that Islamic tradition requires Muslims (who are physically and financially able) to undertake at least once during their lifetimes. Some global health officials fear that, as 2.5 million additional people converge on a single city during a five-day period in October, the stage may be set to turn MERS—which is potentially one mutation away from becoming a more virulent, transmissible disease—into the world’s next pandemic.
Accordingly, scientists are scrambling to understand how a virus that had been circulating in camels for decades suddenly took root in humans and started spreading around the world.
In many ways, MERS is a familiar story, just the latest in a number of newly-discovered pathogens to have landed on the radar of public health officials in recent years. As with nearly two-thirds of emerging diseases—including HIV, SARS, H5N1 (bird flu), and H1N1 (swine flu)—MERS started making trouble for humans after a zoonotic event, or that random moment when it jumped from an animal to humans.
These events are increasingly common, both because they’re being detected more often, and because there’s more and more opportunity for such events to occur, says David Quammen, who has written a book, Spillover: Animal Infections and the Next Human Pandemic on the subject. Interactions between humans and animals have happened forever, but modern development—such as the building of roads and timber camps in tropical forest, or factory farming—has increased the scale and frequency of them. Plus disease can travel much further and faster these days.
Take SARS, or Severe Acute Respiratory Syndrome, the coronavirus that gave the world a scare in 2003 when it infected 8100 people and killed 774 of them in a matter of months.
First identified in China’s Guangdong Province in November 2002, SARS is thought to have originated in bats and been passed to humans by way of the civet, a cat-like animal that was sold in wildlife markets and eaten as a delicacy in parts of China. Once in humans, the virus spread through the air with terrifying speed and reach—most notably when it infected 321 residents of Amoy Gardens, a Hong Kong apartment complex (a 2006 paper on the outbreak found that the virus entered apartments via bathroom floor drains.) The virus ultimately traveled to more than 30 countries, helped along by a handful of “super-spreaders” or individuals who transmit disease particularly effectively. While staying in Hong Kong’s Metropole Hotel, for example, a doctor from Guangdong infected 13 people including those who carried SARS to Canada, Singapore and Vietnam.
然而，对一些人来说，MERS病毒之所以如此可怕，就在于我们不知道它还有多少谜团尚未被发掘。比如最关键的：人类究竟是如何被它感染的，又是如何传染给其他人的。人们已经掌握了一些线索，病骆驼就是其中之一，但目前来看，蝙蝠、骆驼、医院、没有做好防护措施的医护人员、不干净的桌面以及政治因素，都需要为此承担一定责任。一位澳大利亚流行病学专家用“悖论”来描述MERS的扩散，他最近甚至提出，生物恐怖主义也许扮演了推手的角色。
与此同时，自从首次发现人类感染MERS病毒之后的两年以来，相关病例和死亡数一直在持续攀升（而且，现在的世界还笼罩在埃博拉病毒的阴影下）。就在上周，沙特阿拉伯又报告了两起新病例。
世界卫生组织紧急状态委员会已经就MERS召开了6次会议，根据世卫组织的最新计算，35%的感染者都会死亡。不过，虽然MERS已经受到全球医疗团体专家的高度重视，它仍然没有被看作“引起国际关注的突发公共卫生事件”。
尽管如此，由于今年夏天和秋天会有大量朝圣者前往沙特阿拉伯，MERS在人群中引起了不安的骚动。斋月是做小朝（许多穆斯林前往麦加进行的一种宗教仪式）的旺季，7月份，有超过600万人来到沙特阿拉伯。而在10月，全球各地会有更多人来到伊斯兰教的圣城麦加进行大朝——根据伊斯兰教的传统，如果身体和经济状况允许，穆斯林一生中至少需要进行一次大朝。全球卫生部门的一些官员对此感到担忧，因为在10月进行朝觐仪式的5天内，这座城市会涌入250万人。由于MERS病毒可能会突变成更具传染性的恶性病毒，这一盛会也许将使MERS变成全球下一流行性疾病。
相应的，科学家正在努力理解，为何一种在骆驼中传播了几十年的病毒突然找上了人类，并开始在全世界传播。
从许多方面来看，MERS病毒的故事都不陌生，它只是公共卫生部门官员近年来新发现的许多病原体中的最新品种。与包括艾滋病（HIV）、SARS、H5N1（禽流感）和H1N1（猪流感）在内的近三分之二新型疾病一样，MERS也是通过动物传染病或是一些巧合事件，从动物传到人类身上，开始给人类带来困扰。
大卫•奎曼表示，这类事件变得越来越普遍，不仅是因为它们越来越经常被发现，还因为发生这类事件的机会变得越来越多。他就此撰写了一部作品，《致命接触:全球大型传染病探秘之旅》(Spillover: Animal Infections and the Next Human Pandemic）。人类与动物之间的接触一直存在，但是现代社会的发展——比如在热带雨林中修路、搭帐篷，或工厂化的畜牧方式——增加了接触的范围和频率。此外，疾病在现代社会也能传播得更远、更快。
就以SARS（重症急性呼吸综合征）为例。2003年，这种冠状病毒在全世界造成了恐慌。在短短一个月内，就有8,100人受到感染，其中774人最终死亡。
SARS最早于2002年11月在中国广东被确定，人们认为这种病毒来源于蝙蝠，通过果子狸（一种类似猫的动物，在野味市场有售，中国部分地区将其视为美味佳肴）传给了人类。一旦人类感染，这种病毒便可以通过空气以极为恐怖的速度和范围传染——最著名的一次，病毒感染了居住在香港淘大花园的321位居民（2006年一篇研究SARS爆发的论文发现，这种病毒是通过浴室地漏进入公寓的）。SARS病毒最终借助一些“超级传染源”，即特别能够传播该病的个人，进入了超过30个国家。比如，一名来自广东的医生，在留宿香港京华国际酒店(Metropole Hotel)期间将SARS病毒传给了13个人，他们随后将病毒带入了加拿大、新加坡和越南。
SARS was far more transmissible among humans than MERS currently is, but it was also less lethal, killing roughly 10% of its victims compared to the 35% of patients who have died from MERS. This makes MERS a less imminent threat, but also a potentially terrifying one should it mutate into a more transmissible form, an opportunity the virus gets every time it spreads between humans, or from animals to humans.
Watch: Video of virus-sized particle trying to enter cell
But unlike SARS, which is believed to have jumped from humans to animals just a few times, MERS (now that we know it exists) appears to be jumping repeatedly—the spread of the virus propelled along by a number of scattered separate zoonotic events, a pattern that’s mysterious for a number of reasons.
While that puzzle is still being pieced together, it’s likely that this story begins, as SARS did, in a bat. Reservoirs for many a nasty virus (from Ebola to rabies to SARS), bats have a long history of spreading disease—typically through saliva or their tiny droppings—to others in the animal kingdom, from house pets to livestock to humans. In July, scientists published findings that a virus found in the feces of a Cape serotine, a South African bat, was of the same species—and offered the closest genetic match yet—to the MERS-CoV.
Scientists suspect it was a bat that brought MERS to dromedary camels; the animals have tested positive for MERS antibodies dating back to at least 1992 (antibodies are a sign of previous infection). More recently, antibodies have been found in 75% of camels in Saudi Arabia—the virus was active in 35% of them—as well as in camels many countries away in Egypt, Oman, and the Canary Islands off the coast of Spain.
While epidemiologists aren’t certain that the virus’ first leap to humans came via camels, the animal is a likely source. The camel has been proven to be the culprit in at least one instance—that of our 40-something-year-old camel owner near Jeddah. (In late June, a team of Saudi researchers reported in the New England Journal of Medicine that full genome sequences in the virus found in both the human victim and the infected camel were identical.) And the first known patient to die of MERS, a businessman living in Bishah, Saudi Arabia, also had exposure to them: he kept four camels as pets.
The linkage makes sense: On the Arabian Peninsula, where camels are ubiquitous and considered honorable beasts, there is certainly opportunity for zoonotic events.
Slobbering animals even when healthy, camels shed virus through their noses and stool; recent epidemiological research from Qatar also found the milk from many infected camels contained MERS. (It’s unclear whether the milk was infected directly by the camel or contaminated through a calf’s suckling.)
Close contact with the animals, moreover, is hardly rare. A source of livelihood and entertainment, camels in the Middle East are raced like horses and trotted out in beauty pageants (as contestants). They’re regularly consumed for milk and meat, sometimes in the raw forms that have been flagged as possible transmission routes. Kept as pets and livestock, owners are intimately involved in the feeding, care and birthing of the creatures, contact that the WHO and a number of governments now advise be done with facial masks and gloves. (Offended by such guidance and the suggestion the animal has anything to do with transmitting a lethal disease, some Saudis, particularly loyal to the animal, have posted videos of themselves on YouTube kissing camels.)
But if camels are the zoonotic link, then it raises another, perhaps bigger mystery: why didn’t MERS jump sooner? Here, the best answer, epidemiologists say, is that it almost certainly did—we just didn’t notice.
At least one MERS outbreak—which infected 13 people in a Jordan hospital in May 2012 and was discovered in hindsight—predates the discovery of MERS (at the time, doctors in Jordan believed the illness to be pneumonia). Recent surveillance efforts in Saudi Arabia and Qatar have also turned up a number of individuals who either have MERS antibodies (meaning they once had the virus) or are asymptomatic—meaning they have the virus but show no sign of it—suggesting there are far more cases than officially tallied.
As scary as MERS is—and Ebola, too, for that matter—most infectious disease experts say the outbreaks are cause for cautious vigilance, not panic. What keeps them up at night, rather, is the next one.
SARS在人群中的传染性比目前的MERS强得多，但它的致命性却较弱，只有10%的感染者死亡，而MERS则有35%。因此MERS目前虽然不是紧迫的威胁，但也具有潜在的危险性，一旦病毒产生更具传染性的变种，就随时可能在人类之间或动物和人类之间传播。
相关视频：病毒大小的粒子试图进入细胞
不过与据信只会在人类和动物间传播几次的SARS病毒不同，MERS病毒（现在我们都知道它存在了）似乎可以不断跳越物种——这种病毒通过许多种不同的动物传染病事件实现了扩散，这一传染模式十分不可思议。
人们在拼凑谜底的过程中，发现似乎这一病毒同SARS一样，源头来自蝙蝠。蝙蝠带有许多糟糕的病毒（从埃博拉病毒，到狂犬病毒，再到SARS病毒），动物王国拥有向宠物、牲畜和人类传播病毒的悠久历史——通常通过唾液或排泄物。今年7月，科学家发布的最新研究报告显示，在南非翼足棕蝠的排泄物中发现了一种病毒，与MERS病毒属于同种，拥有迄今为止最为匹配的基因。
科学家怀疑是蝙蝠将MERS传给了单峰骆驼。动物们的MERS抗体呈阳性的情况至少可以追溯到1992年（产生抗体即说明曾经遭到感染）。最近，有75%的沙特阿拉伯骆驼都被检测出了病毒抗体——其中35%的骆驼身上仍有活跃的病毒。而远到埃及、阿曼、以及西班牙的加那利群岛的骆驼上也带有抗体。
流行病学专家还不确定病毒是否首先是由骆驼传给人类的，但这是一个可能的源头。至少在一起事件中，骆驼被证明是罪魁祸首——即上文开篇提到的那头骆驼的主人。【6月底，沙特阿拉伯的一个研究小组在《新英格兰医学杂志》（New England Journal of Medicine）上发表文章称，死者和被感染的骆驼身上的病毒的全部基因组序列完全相同。】而已知的第一个死于MERS的患者（一个住在沙特阿拉伯比沙的商人）也与骆驼有着亲密接触：他豢养了4头骆驼作为宠物。
这种联系是讲得通的：在阿拉伯半岛，骆驼无所不在，被认为是高贵的动物，这显然给动物传染病提供了机会。
即便是健康的骆驼也会流唾液，它们还会通过鼻子和粪便传播病毒。卡塔尔流行病学专家最近通过研究发现，许多受感染的骆驼奶中也包含MERS病毒。（不过目前尚不明白，究竟是骆驼奶直接被污染了，还是由于小骆驼的吮吸而遭到污染。）
此外，与动物的亲密接触也并不罕见。骆驼在中东作为营生和娱乐的来源之一，通常被当作马一样使用，并作为选美比赛的选手出场。骆驼奶和骆驼肉都可食用，有时这些未经加工的产品就是病毒可能的传播途径。主人们将骆驼看作宠物和牲口，会在喂食、看护和接生时与它们亲密接触。而世界卫生组织和许多政府已经建议人们在做这些事情时戴好面罩和手套。（一些沙特阿拉伯人，尤其是热爱骆驼的人，认为将骆驼看作传播致命疾病的嫌疑犯并提出这样的指南和建议，是一种对他们的冒犯。他们在YouTube上发布了亲吻骆驼的视频表示抗议。）
不过，如果骆驼是动物传染病的一环，那就产生了另一个更大的疑问：为何MERS病毒没有早些时候跨物种传播呢？流行病学专家表示，该问题最好的答案是，它几乎毫无疑问地确实被传播了，只是我们没有发现而已。
至少有一次MERS的爆发——2012年5月，在约旦一家医院中，有13人被感染，事后才被发现——早于MERS病毒的发现（当时，约旦的医生认为那是肺炎症状）。最近，沙特阿拉伯和卡塔尔的监测也发现有许多人拥有MERS抗体（即曾经被MERS感染过），或是无症状感染者，即携带病毒但没有出现症状。这意味实际MERS的感染病例数远远多于官方记录的数目。
尽管MERS病毒和埃博拉病毒十分可怕，但大多数传染病专家都表示，疾病爆发将会让他们愈发谨慎和小心，而不是恐惧。而让他们睡不着觉的，永远是下一种病毒。（财富中文网）
译者：严匡正
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