????從外表的各種跡象來看，這頭駱駝是感冒了。沙特阿拉伯吉達一個谷倉共有九頭駱駝，這是其中之一。它病了，不斷地流鼻涕。駱駝的主人已經傾盡所能，他將手指蒙上蒸汽熏過的濕布，伸進駱駝的鼻孔里擦拭。

????7天后，駱駝的主人（據消息源說，年齡是43歲或44歲）開始感覺疲倦，流鼻涕并且咳嗽不止。隨后5天，他發現自己越來越喘不過氣。3天后，他因為嚴重的呼吸短促被送進重癥護理病房（ICU），并于15天后死亡。這件事發生在去年11月。

????而駱駝康復了。

????事實證明，那頭流鼻涕的駱駝根本沒有感冒，而是患上了MERS，即中東呼吸系統綜合征（Middle East Respiratory Syndrome）。也正是這個病毒，在4個半星期后奪去了它主人的生命。這或許是第72例記錄在案的MERS受害者。

????MERS病毒在駱駝身上相對普遍，而且是良性的。它與重癥急性呼吸綜合征（SARS）病毒和引起普通感冒的病毒同屬于冠狀病毒，并于2012年9月首次威脅到人類的生命。從那時起，這種形似釘子，只有幾納米長的致命病毒，就慢慢地開始在全球擴散：根據世界衛生組織（World Health Organization）發布的已經過實驗室確認的數據，MERS病毒已經至少感染了837人，造成其中291人死亡。

????大多數病例發生在阿拉伯半島（沙特阿拉伯報告的感染死亡數比世界衛生組織還要多，有723例感染，299例死亡），不過也有病人出現在遠離吉達的20多個國家，包括遠離中東的法國、馬來西亞，甚至美國印第安納州明斯特市。（去年4月，一位曾經在沙特阿拉伯醫療機構工作過的美國居民，走進了明斯特的社區醫院急診室。由于醫院處理得當，看護有方，這位病人最終痊愈出院。）

????今年春天，感染者的增速尤其驚人。根據歐洲疾病控制與預防中心（European Centers for Disease Control and Prevention，其作用相當于美國疾病控制與預防中心）的數據，單單今年4月報告的全球新增MERS病例，就超過了前兩年病例數的總和。而在沙特阿拉伯衛生部長下臺不久后的6月初，該國衛生部就宣布病例數甚至比之前想象的更高，并表示前任部長至少漏報了113起病例（其中有92人現已死亡）。

????埃博拉病毒（Ebola）近來讓全球陷于恐慌之中，不過在今年早些時候，病例在各大洲激增的MERS病毒才是讓全球衛生部門的官員最為頭疼的。今年夏天，病情的蔓延趨勢有所減緩，但病原體并未消失，更讓人擔憂的是，流行病學專家至今還沒有把它徹底搞清。

????無論是疾病還是怪誕的社會潮流，傳染所具有的神奇魔力和不可預知性，一直讓熱愛科學和創新的人群深深著迷。在《財富》（Fortune）工作的我們也不例外。在這一系列短文中，我和我的同事將追尋各種不同的“突然蔓延”——從MERS病毒到不那么致命的并購傳言、市場恐慌、圖書銷售以及當代“自拍”現象——希望更好地了解它們。一些趨勢的蔓延更容易用科學來解釋。人們也認為MERS病毒能夠像埃博拉病毒一樣，屬于科學能夠解釋的那一類。

????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.