《财富》最新专题：传染

    它最早起源于中国或蒙古的某个地方，仿佛像一只突然从黄沙中钻出来的蚱蜢。它沿着丝绸之路，跨过广阔的欧洲大草原，横穿安那托利亚半岛，最后来到位于黑海之滨的克里米亚。所到之处，死亡如影随形。

    黑海之滨的卡法港一度是热那亚商人的贸易前哨地。这场瘟疫爆发后，热那亚商人们抱头鼠窜地跳上商船，通过黑海狂奔回马尔马拉海，然后进入地中海。但不知不觉地，他们也带回了瘟疫。死神随着他们下船登岸，从热那亚、威尼斯、墨西拿的西西里镇一直扫荡到法国的马赛。隐藏在东方鼠蚤肠胃内的鼠疫杆菌随同其猎物（黑家鼠）的血液四处传播，同时也进入每一个被感染的人体内。

    这种病菌有多种症状体征，比如淋巴腺肿大、肺炎、败血症等等。这三种症状都有发病快、痛苦、致死率高的特点，很多病人的腹股沟、腋下、颈部淋巴都会冒出肿瘤。每天都有几千人死亡。

    It had started somewhere in China, or Mongolia perhaps, emerging like an ancient locust from the soil. Shadowing the Silk Road, it had crossed the vast Eurasian steppe, traversed the Anatolian peninsula, and arrived in Crimea on the Black Sea. Everywhere, death had followed.

    At the Black Sea port of Caffa, where merchants from the Italian city of Genoa had set up a trading outpost, the pestilence landed with a fury. The Genoese fled to their ships, racing back through the Black Sea, to the Sea of Marmara, then to the Mediterranean. Unknowingly, they brought the sickness and fury with them. From ship to port—Genoa, Venice, the Sicilian town of Messina, the French harbor of Marseille—the microscopic Yersinia pestis followed, hiding in the stomachs of Oriental rat fleas, circulating in the blood of their prey, the black rat, and within each new human being infected.

    The illness came in various forms—bubonic, pneumonic, septicemic. All three were swift, painful and gruesome, with many of the victims developing oozing tumors in their groins, armpits, or necks.

    仅仅几周时间，这种疾病就蔓延到了第勒尼安海的贸易重镇比萨。不到几个月，它便横扫西班牙东部和法德两国。所到之处，十室九空。来自法国加斯科尼的海船又把它载到了英国南端一个名叫梅尔库姆里吉斯的小港口，它从这里登陆，杀向人口众多的英国西部港市布里斯托，一个月后传播到了伦敦。不久后，整个不列颠群岛，加上挪威、丹麦，甚至东到俄罗斯，都成了它的肆虐之所。

    它就是欧洲人谈之色变的“黑死病(The Black Death)”。或许更适合的名称应该是“大死亡(Great Mortality)”。在14世纪中叶大约5年的时间里，这种神秘的瘟疫导致数千万人丧命，也就是说，死神的镰刀一举划掉了当时整个欧洲四分之一到一半的人口。

    黑死病其实并不是第一起在全球范围内大规模流行的瘟疫。在此之前约8个世纪，查士丁尼大瘟疫大约导致1亿人丧命，这种瘟疫据说也是鼠疫。同时黑死病也不是鼠疫在人类历史上最后一次肆虐。第三次鼠疫大流行又叫“现代瘟疫”，起源于19世纪60年代的中国，至少导致了1000万人死亡。

    那么，这些瘟疫究竟是由什么触发的？奥斯陆大学（University of Oslo）生物学家尼尔斯•克里斯蒂安•斯坦瑟斯及其同事指出，鼠疫病菌的宿主生物在全球各地都不鲜见（见下图），而且偶发的鼠疫病例直到今年夏天还曾在中国和美国出现，去年12月，马达加斯加也出现了人感染鼠疫的病例。那么这是否意味着黑死病或许又将卷土重来？如果答案是肯定的，这次它会流传多广？

    It took only weeks for the disease to arrive in Pisa, a center of trade on the Tyrrhenian Sea. It took mere months to carve through Eastern Spain, France and Germany, slicing through the population as if clear-cutting a forest. Ships from Gascony in Southwestern France hauled the disease to Melcombe Regis, a small seaport on England’s southern flank. From there, it was carried to crowded Bristol, a month later to London, and before long to all the British Isles, Norway, Denmark, as far east as Russia.

    “The Black Death,” it was called; yet even more fitting was the name, the “Great Mortality”: Over the course of some five years in the mid-14th century, the mysterious plague claimed the lives of tens of millions of people—a reign of terror that, by most assessments, killed between a quarter and half the population of Europe.

    This wasn’t the first time a massive, globe-spanning pandemic had taken hold: Eight centuries earlier, the Justinian plague—ostensibly caused by the same microbe—had killed an estimated 100 million people. Nor would it be the last devastating outbreak of Y. pestis. A third major pandemic, the so-called Modern Plague, began in China in the 1860s and claimed at least 10 million lives before it was through.

    What triggered any of them? University of Oslo biologist Nils Christian Stenseth and colleagues have shown that reservoirs of the plague bacteria remain common in much of the world (see map below). And sporadic cases of bubonic plague have popped up as recently as this summer in the U.S., and in China, as they did in Madagascar in December. Could another Black Death take hold and, if so, how far would it spread?