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COVID-19 coronavirus epidemic has a natural origin
COVID-19冠状病毒的自然起源
The novel SARS-CoV-2 coronavirus is the product of natural evolution, according to findings published in the journal Nature Medicine.
根据发表在《自然-医学》杂志上的发现，新型SARS-CoV-2冠状病毒是自然进化的产物。
The analysis of public genome sequence data from SARS-CoV-2 and related viruses found no evidence that the virus was made in a laboratory or otherwise engineered.
对SARS-CoV-2及其相关病毒的公共基因组序列数据进行分析，没有发现任何证据表明该病毒是在实验室制造或以其他方式设计的。
Authors on the paper include Kristian Andersen, PhD, an associate professor of immunology and microbiology at Scripps Research Robert F. Garry, of Tulane University; Edward Holmes, of the University of Sydney; Andrew Rambaut, of University of Edinburgh; W. Ian Lipkin, of Columbia University.
论文的作者包括、斯克里普斯研究所的免疫学和微生物学副教授克里斯汀·安德生博士、杜兰大学的罗伯特·F·加里、悉尼大学的爱德华·霍姆斯、爱丁堡大学的安德鲁·兰巴特、哥伦比亚大学的W·伊恩·利普金。
Coronaviruses are a large family of viruses. The first known severe illness caused by a coronavirus emerged with the 2003 Severe Acute Respiratory Syndrome (SARS) epidemic in China. A second outbreak of severe illness began in 2012 in Saudi Arabia with the Middle East Respiratory Syndrome (MERS).
冠状病毒是一个大家族的病毒。由冠状病毒引起的第一个已知的严重疾病是2003年中国的严重急性呼吸系统综合征（SARS）。第二次严重疾病爆发始于2012年沙特阿拉伯的中东呼吸综合征（MERS）。
The scientists analyzed the genetic template for spike proteins, armatures on the outside of the virus that it uses to grab and penetrate the outer walls of human and animal cells. More specifically, they focused on two important features of the spike protein: the receptor-binding domain (RBD), a kind of grappling hook that grips onto host cells, and the cleavage site, a molecular can opener that allows the virus to crack open and enter host cells.
科学家们分析了spike蛋白的基因，S蛋白是病毒外部的盔甲，用来抓住并穿透人和动物细胞膜。更具体地说，他们着重研究了棘突蛋白的两个重要特征：受体结合域（RBD），一种抓住宿主细胞的钩状物，以及裂解位点，类似开罐器，病毒借此打开细胞膜上并进入宿主细胞。
The scientists found that the RBD portion of the SARS-CoV-2 spike proteins had evolved to effectively target a molecular feature on the outside of human cells called ACE2, a receptor involved in regulating blood pressure. The SARS-CoV-2 spike protein was so effective at binding the human cells, in fact, that the scientists concluded it was the result of natural selection and not the product of genetic engineering.
科学家们发现，SARS-CoV-2 S蛋白的RBD部分已经进化成能有效靶向人类细胞外一种叫做ACE2的分子，ACE2是一种参与调节血压的受体。S蛋白在结合人类细胞方面非常有效，事实上，科学家们认为这是自然选择的结果，而不是基因工程的产物。
This evidence for natural evolution was supported by data on SARS-CoV-2's backbone -- its overall molecular structure. If someone were seeking to engineer a new coronavirus as a pathogen, they would have constructed it from the backbone of a virus known to cause illness. But the scientists found that the SARS-CoV-2 backbone differed substantially from those of already known coronaviruses and mostly resembled related viruses found in bats and pangolins.
这一自然进化的证据得到了有关SARS-CoV-2骨架分子结构数据的支持。如果有人想制造一种新的冠状病毒作为病原体，他们可能是从一种已知能致病的病毒的骨架上构建出来的。但是科学家们发现，SARS-CoV-2的骨架与已知的冠状病毒有很大的不同，并且大部分与蝙蝠和穿山甲中发现的相关病毒相似。
These two features of the virus, the mutations in the RBD portion of the spike protein and its distinct backbone, rules out laboratory manipulation as a potential origin for SARS-CoV-2.
病毒的这两个特征，即spike蛋白RBD部分的突变及其独特的骨架，排除了实验室操作可能是SARS-CoV-2的来源。
Based on their genomic sequencing analysis, Andersen and his collaborators concluded that the most likely origins for SARS-CoV-2 followed one of two possible scenarios.
根据他们的基因组测序分析，安德生和他的合作者得出结论，SARS-CoV-2最可能的起源遵循两种可能的情况之一。
In one scenario, the virus evolved to its current pathogenic state through natural selection in a non-human host and then jumped to humans. This is how previous coronavirus outbreaks have emerged, with humans contracting the virus after direct exposure to civets (SARS) and camels (MERS). The researchers proposed bats as the most likely reservoir for SARS-CoV-2 as it is very similar to a bat coronavirus. There are no documented cases of direct bat-human transmission, however, suggesting that an intermediate host was likely involved between bats and humans.
在一个场景中，病毒通过在非人类宿主中的自然选择进化到目前的致病状态，然后跳到人类身上。这就是以前冠状病毒爆发的原因，人类在直接接触到麝香猫（SARS）和骆驼（MERS）后感染了冠状病毒。研究人员认为蝙蝠是SARS-CoV-2最可能的宿主，因为它与蝙蝠冠状病毒非常相似。然而，目前还没有关于蝙蝠与人类直接传播的记录，这表明蝙蝠和人类之间可能存在一种中间宿主。
In the other scenario, a non-pathogenic version of the virus jumped from an animal host into humans and then evolved to its current pathogenic state within the human population. For instance, some coronaviruses from pangolins, armadillo-like mammals found in Asia and Africa, have an RBD structure very similar to that of SARS-CoV-2. A coronavirus from a pangolin could possibly have been transmitted to a human, either directly or through an intermediary host such as civets or ferrets.
另一个可情景是，非致病性病毒从动物宿主跳到人类，然后在人类种群中进化到其当前的致病状态。例如，一些穿山甲冠状病毒（亚洲和非洲发现的类似犰狳的哺乳动物）的RBD结构与SARS-CoV-2非常相似。穿山甲的冠状病毒可能直接或通过中间宿主如麝香猫或雪貂传播给人类。
Study co-author Andrew Rambaut cautioned that it is difficult if not impossible to know at this point which of the scenarios is most likely. If the SARS-CoV-2 entered humans in its current pathogenic form from an animal source, it raises the probability of future outbreaks, as the illness-causing strain of the virus could still be circulating in the animal population and might once again jump into humans. The chances are lower of a non-pathogenic coronavirus entering the human population and then evolving properties similar to SARS-CoV-2.
这项研究的合著者安德鲁·兰巴特警告说，在这一点上，很难甚至不可能知道哪种情况最有可能发生。如果SARS-CoV-2以目前的致病形式从动物源进入人类，它将增加未来爆发的可能性，因为致病病毒株仍可能在动物群中传播，并可能再次跳入人类体内。非致病性冠状病毒进入人群的几率较低，然后进化出类似于SARS-CoV-2的特性。
重点词汇学习
1.armature n. 电枢（电机的部件）；盔甲，甲胄；防卫器官
2.civet n. 灵猫，麝猫(分布于中非和亚洲); 麝猫香，灵猫香(用于制作香水);
3.pangolin穿山甲
4.armadillo [ˌɑːrməˈdɪloʊ] . 犰狳(美洲动物，体表覆盖甲冑状原骨质板，以昆虫为食，遭攻击时缩成一团)
5.intermediate host 中间宿主。
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