????然而，對一些人來說，MERS病毒之所以如此可怕，就在于我們不知道它還有多少謎團尚未被發(fā)掘。比如最關鍵的：人類究竟是如何被它感染的，又是如何傳染給其他人的。人們已經(jīng)掌握了一些線索，病駱駝就是其中之一，但目前來看，蝙蝠、駱駝、醫(yī)院、沒有做好防護措施的醫(yī)護人員、不干凈的桌面以及政治因素，都需要為此承擔一定責任。一位澳大利亞流行病學專家用“悖論”來描述MERS的擴散，他最近甚至提出，生物恐怖主義也許扮演了推手的角色。

????與此同時，自從首次發(fā)現(xiàn)人類感染MERS病毒之后的兩年以來，相關病例和死亡數(shù)一直在持續(xù)攀升（而且，現(xiàn)在的世界還籠罩在埃博拉病毒的陰影下）。就在上周，沙特阿拉伯又報告了兩起新病例。

????世界衛(wèi)生組織緊急狀態(tài)委員會已經(jīng)就MERS召開了6次會議，根據(jù)世衛(wèi)組織的最新計算，35%的感染者都會死亡。不過，雖然MERS已經(jīng)受到全球醫(yī)療團體專家的高度重視，它仍然沒有被看作“引起國際關注的突發(fā)公共衛(wèi)生事件”。

????盡管如此，由于今年夏天和秋天會有大量朝圣者前往沙特阿拉伯，MERS在人群中引起了不安的騷動。齋月是做小朝（許多穆斯林前往麥加進行的一種宗教儀式）的旺季，7月份，有超過600萬人來到沙特阿拉伯。而在10月，全球各地會有更多人來到伊斯蘭教的圣城麥加進行大朝——根據(jù)伊斯蘭教的傳統(tǒng)，如果身體和經(jīng)濟狀況允許，穆斯林一生中至少需要進行一次大朝。全球衛(wèi)生部門的一些官員對此感到擔憂，因為在10月進行朝覲儀式的5天內(nèi)，這座城市會涌入250萬人。由于MERS病毒可能會突變成更具傳染性的惡性病毒，這一盛會也許將使MERS變成全球下一流行性疾病。

????相應的，科學家正在努力理解，為何一種在駱駝中傳播了幾十年的病毒突然找上了人類，并開始在全世界傳播。

????從許多方面來看，MERS病毒的故事都不陌生，它只是公共衛(wèi)生部門官員近年來新發(fā)現(xiàn)的許多病原體中的最新品種。與包括艾滋病（HIV）、SARS、H5N1（禽流感）和H1N1（豬流感）在內(nèi)的近三分之二新型疾病一樣，MERS也是通過動物傳染病或是一些巧合事件，從動物傳到人類身上，開始給人類帶來困擾。

????大衛(wèi)?奎曼表示，這類事件變得越來越普遍，不僅是因為它們越來越經(jīng)常被發(fā)現(xiàn)，還因為發(fā)生這類事件的機會變得越來越多。他就此撰寫了一部作品，《致命接觸:全球大型傳染病探秘之旅》(Spillover: Animal Infections and the Next Human Pandemic）。人類與動物之間的接觸一直存在，但是現(xiàn)代社會的發(fā)展——比如在熱帶雨林中修路、搭帳篷，或工廠化的畜牧方式——增加了接觸的范圍和頻率。此外，疾病在現(xiàn)代社會也能傳播得更遠、更快。

????就以SARS（重癥急性呼吸綜合征）為例。2003年，這種冠狀病毒在全世界造成了恐慌。在短短一個月內(nèi)，就有8,100人受到感染，其中774人最終死亡。

????SARS最早于2002年11月在中國廣東被確定，人們認為這種病毒來源于蝙蝠，通過果子貍（一種類似貓的動物，在野味市場有售，中國部分地區(qū)將其視為美味佳肴）傳給了人類。一旦人類感染，這種病毒便可以通過空氣以極為恐怖的速度和范圍傳染——最著名的一次，病毒感染了居住在香港淘大花園的321位居民（2006年一篇研究SARS爆發(fā)的論文發(fā)現(xiàn)，這種病毒是通過浴室地漏進入公寓的）。SARS病毒最終借助一些“超級傳染源”，即特別能夠傳播該病的個人，進入了超過30個國家。比如，一名來自廣東的醫(yī)生，在留宿香港京華國際酒店(Metropole Hotel)期間將SARS病毒傳給了13個人，他們隨后將病毒帶入了加拿大、新加坡和越南。

????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.