Viruses have spread among humans for many years

As COVID-19 has hitchhiked around the globe, causing lockdowns, pneumonia and fear, scientists have been racing to determine where the SARS-CoV-2 coronavirus has come from.
新冠病毒在全球传播，导致多地封城，并引发了肺炎和恐慌，科学家们一直在努力确定新冠病毒的来源。
While we don’t have all the answers yet – including whether it came from an animal reservoir – a new analysis has definitively put to rest the conspiracies that claim it’s a lab-made disease.
虽然我们还没有弄清所有问题，如病毒是否来自动物宿主，但新的分析结果的确终结了病毒来自于实验室的说法。
The study raises some interesting possibilities regarding the origin of the new coronavirus. One of the scenarios suggests the virus may have been circulating harmlessly in human populations for quite a while before it became the pandemic that’s now stopped the world in its tracks.
这项研究针对新冠病毒的来源提出了几种有趣的可能性。其中一种设想是病毒可能已经在人类中无害传播了很久，然后才发展成了疫情，导致世界停滞不前。
“It is possible that a progenitor of SARS-CoV-2 jumped into humans, acquiring [new genomic features] through adaptation during undetected human-to-human transmission,” the team from the US, UK and Australia writes in the study.
这个来自美国、英国和澳大利亚的团队在研究中写道：“可能最初的新冠病毒进入人体以后，在未被发现的人际传播中为了适应人体环境获得了‘新的基因组特征’。”
“Once acquired, these adaptations would enable the pandemic to take off and produce a sufficiently large cluster of cases.”
“一旦获得了‘新的基因组特征’，就会爆发疫情，产生一个足够大的病例群。”
The researchers analysed genomic data available from SARS-CoV-2 and other similar coronaviruses, showing that the receptor-binding domain (RBD) sections of SARS-CoV-2 spike proteins were so effective at binding to human cells, they had to be caused by natural selection.
研究人员分析了从新冠病毒和其他类似的冠状病毒中获取的基因组数据，发现新冠病毒刺突蛋白的受体结合区和人体细胞能有效结合，这些都要通过自然选择实现。
“By comparing the available genome sequence data for known coronavirus strains, we can firmly determine that SARS-CoV-2 originated through natural processes,” said one of the researchers, immunologist Kristian Andersen at Scripps Research.
参与这项研究的斯克利普斯研究所的免疫学家Kristian Andersen说：“通过比较已知冠状病毒毒株可用的基因组序列数据，我们可以确定新冠病毒源于自然过程。”
“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.”
“这个病毒的两个特点，刺突蛋白的受体结合区和它的主干的突变，都排除了实验室操作是新冠病毒潜在来源的可能性。”