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。
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）。
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.