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一篇关于伦敦一处墓地出土的骨头与牙齿的研究的论文不仅得出了黑死病确切的病源是鼠疫耶尔森菌——正是这种菌导致了腺鼠疫——的结论，而且揭示出这种中世纪时代的菌种是现代所有鼠疫菌种唯一的祖先。上述研究是由来自加拿大麦克马斯特（McMaster）大学的Kirsten Bos以及来自于德国Tubingen大学的Verena Schuenemann共同领导的团队完成的。本周的“自然”杂志发表了这篇论文。 The theory the Black Death was a type of bubonic plague, long taken for granted, was challenged ten years ago by Christopher Duncan and Susan Scott of the University of Liverpool. Dr Duncan and Dr Scott saw discrepancies between the way that the Black Death spread through 14th-century Europe and the behaviour of more recent episodes of plague. Their hypothesis was that the 14th-century epidemic was caused by a virus which spread directly from person to person, rather than by Y. pestis, which is a bacterium spread by rats’ fleas. They made this argument in a book called “Biology of Plagues: Evidence from Historical Populations”, which was published in 2001. 长久以来，人们都理所当然地把黑死病看作是一种腺鼠疫。但是在十多年之前，利物浦大学的两位学者 Christopher Duncan 和 Susan Scott提出了不同见解，他们发现席卷14世纪欧洲的黑死病与年代更近一些的鼠疫在传播方式上有不同之处。他们的推测在14世纪的欧洲是由人间传播的病毒导致疫病流行，而并非是由鼠类身上的跳蚤传播的鼠疫耶尔森菌引起。他们将这个观点结集成一本书，书名为《鼠疫生物学：历史人口中的证据》，于2001年出版。 Dr Duncan’s and Dr Scott’s scepticism was based on the fact that the Black Death, which killed about a third of Europe’s population, spread throughout the continent far faster than modern plague spreads. That suggests a different method of transmission, and possibly a different pathogen entirely. Based on the medieval descriptions of the dark spots on the skin that gave the Black Death its name, they suggested the epidemic was actually a viral haemorrhagic fever, similar to modern Ebola. Duncan和Scott博士的论点主要是基于以下事实：当年差点害死1/3欧洲人口的黑死病的传播速度要远远高于现代鼠疫的传播速度。这一事实表明当年黑死病传播方式是不同的，可能存在完全不同的病原体。黑死病名称来源于中世纪对这一疾病的描述：皮肤上出现黑点……，据此两位学者认为黑死病可能是一种病毒性出血热，有点儿像现代的埃博拉病毒。 Dr Bos and Dr Schuenemann definitively knock this idea on the head. They have sequenced DNA extracted from the dental pulp of bodies buried in East Smithfield, part of the City of London. The genome is that of Y. pestis. Historical evidence dates the grave to the end of 1348 or the beginning of 1349—the height of the Black Death—and suggests the site was specifically for the burial of its victims. Bos博士和Schuenemann博士对此深信不疑。他们提取了从以前伦敦所属的东Smithfield挖出的尸体身上的牙髓，对其作了DNA测序。检出鼠疫耶尔森菌基因来。历史记载了这片坟墓的埋葬时间是1348年末到1349年初，正值黑死病高发期，这就表明了这片墓地专门用来埋葬黑死病死者。 But that is not all. The paper also suggests that every existing strain of Y. pestis can be traced to the Black Death, and not to the Plague of Justinian, a series of epidemics which hit Europe in the sixth, seventh and eighth centuries, as had been previously thought. The authors of the paper believe that these outbreaks were either caused by a completely different variety of Y. pestis, not now present in humans, or were of a different disease altogether, and therefore cannot be linked to modern cases of bubonic plague. 这还不是研究结果的全部。这篇文章同时指出现存任何一种鼠疫耶尔森菌都可以追溯到黑死病时期的病菌，而非以前人们所认为的曾经在6世纪7世纪和8世纪在欧洲大流行的查士丁尼瘟疫的病菌。文章的作者相信查士丁尼瘟疫有两种可能：一是一种和现在人间传播的完全不同的鼠疫耶尔森菌的变种，二是一种完全不同的疾病，和现代的腺鼠疫没有任何联系。 The Black Death, then, seems to have been a new disease in the 14th century, to which no historical resistance would have existed. That goes some way to explaining the speed of its dispersal and the severity of its symptoms—just as smallpox hit Amerindian populations particularly severely when that virus was first introduced into the Americas by European explorers. Later outbreaks of plague would have occurred in a population which had grown more used to the pathogen, and had both primed immune systems and evolved resistance caused by those with genetic protection against the disease having survived it. 因此，在15世纪，黑死病对于人们来说是一种全新的疾病，人类对其还未曾积累任何抵抗力。这就能够从某种意义上解释它的传播速度和并发症的严重程度。当年由欧洲探险家们带到美洲的天花病毒在袭击毫无抵抗力的美洲印第安人时出现的严重程度与此类似。由于有些受传染而又幸存下来的人身上自然产生了基因抗体，因此其后的瘟疫的爆发就是在已经部分适应这些病原体，并且已经拥有抗原免疫系统和进化了的防御系统的人群中传播了。所以传播效果就大有不同。 Other differences between the strain of Y. pestis found in Smithfield and more modern cases, which have been used to question the theory that bubonic plague was responsible for the Black Death, are also addressed by the paper. They could be explained by factors such as the genetics of the host population, social conditions and climate, and also by the fact that over the centuries the microbe itself has evolved, and thus changed in virulence. 本文还提到了，过去长久以来作为质疑黑死病就是腺鼠疫的主要证据的是从Smithfield发现的鼠疫耶尔森菌和距现代更近发现的鼠疫菌存在很多不同。这篇文章揭示导致这些不同的因素来自于俗主人群的基因，社会情况和气候状况等。甚至由于过去的这些世纪以来病菌自身也在进化中，因此病毒力有所变化。 As well as confirming the status of Y. pestis as the cause of the Black Death, this paper brings to light new information about a disease which still results in deaths today. It also helps to explain some of the differences between modern plague and its medieval forerunner. 本文除了肯定黑死病的致病源就是鼠疫耶尔森菌之外，还揭示了这种至今仍然致命的疾病的其他一些新信息。这有助于解释现代瘟疫与中世纪时期流行疾病的不同之处。 |
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